Mound Cake Recipe with Cake Mix and Coconut Filling

This Mound cake is a chocolate cake-mix dessert with a sweet coconut filling and a smooth chocolate topping, inspired by the familiar chocolate-and-coconut candy combination. The cake is easy to assemble in a 9-by-13-inch pan, and poking holes in the warm cake lets the creamy filling settle into each slice.

Ingredients

For the cake: 1 box (15.25 oz / 432 g) chocolate cake mix, plus the ingredients listed on the package; for a typical mix, use 3 large eggs, 1 cup (240 ml) water, and 1/2 cup (120 ml) neutral oil.
Nonstick cooking spray or 1 teaspoon (5 ml) neutral oil, for the baking pan.
For the coconut filling: 1 can (14 oz / 396 g) sweetened condensed milk.
2 cups (about 170 g) sweetened shredded coconut.
1 teaspoon (5 ml) vanilla extract.
1/8 teaspoon (about 0.5 g) fine salt.
For the chocolate topping: 12 oz (340 g) semisweet chocolate, finely chopped or in small chips.
1 1/2 cups (360 ml) heavy cream.
Optional garnish: 2 tablespoons (about 10 g) toasted shredded coconut.

Instructions

Prepare the pan and oven. Heat the oven to 350°F (177°C). Lightly coat a 9-by-13-inch (23-by-33-cm) baking pan with cooking spray or oil. Check the cake-mix package before starting: the quantities above suit many standard-size chocolate mixes, but use the package’s specified egg, water, and oil amounts if they differ. This keeps the cake’s texture on track.
Mix and bake the cake. Combine the cake mix and its required ingredients in a large bowl. Beat with a hand mixer on medium speed for about 2 minutes, or whisk thoroughly until the batter is smooth and no dry pockets remain. Pour it into the prepared pan and level the top. Bake for about 28 to 32 minutes, checking at the earliest time given on the box. A toothpick inserted near the center should come out clean or with a few moist crumbs, not wet batter. Set the pan on a heat-safe surface.
Make the coconut filling. While the cake bakes, stir the sweetened condensed milk, shredded coconut, vanilla, and salt together in a medium bowl. The mixture should be thick and evenly moistened, not runny. If the coconut is packed tightly in the measuring cup, fluff it first and spoon it in rather than pressing it down; too much coconut can make the filling dry and difficult to spread.
Make holes and add the filling. As soon as the cake comes out of the oven, use the rounded handle of a wooden spoon to poke holes across the surface, spacing them about 1 inch (2.5 cm) apart. Press down to roughly two-thirds of the cake’s depth without piercing the bottom. Spoon the coconut mixture over the warm cake and gently spread it into an even layer, nudging some filling into the holes. Work carefully so you do not tear up the cake.
Cool the cake. Leave the cake in its pan at room temperature for about 1 hour, until it is no longer warm to the touch. This gives the filling time to settle and keeps heat from melting the chocolate topping. Do not put a hot pan directly into the refrigerator; it can warm nearby foods and create excess condensation.
Prepare and spread the topping. Put the chopped chocolate in a heat-safe bowl. Warm the cream in a small saucepan over medium-low heat until steaming, with small bubbles at the edge; do not let it boil. Pour the cream over the chocolate, wait 3 minutes, then stir slowly from the center outward until glossy and smooth. Pour the ganache over the cooled cake and spread it to the edges. If it seems very thin, let it stand for a few minutes, stirring once, before spreading.
Chill before slicing. Refrigerate the cake uncovered for about 45 minutes, or until the topping is set enough to cut neatly. Sprinkle with toasted coconut if you like. For clean slices, use a sharp knife warmed under hot water and wiped dry between cuts. Keep the cake refrigerated after serving.

Tips

Use the box as a guide for the batter. Cake-mix sizes and formulas vary. The amounts listed are a practical starting point for a 15.25-ounce (432-g) mix, but the directions on your box take priority. If your package calls for a different amount of liquid or eggs, follow it rather than trying to force the listed example quantities.
Choose the right coconut. Sweetened shredded coconut makes the filling tender and candy-like. Unsweetened coconut works, but the filling will taste less sweet and may feel drier; stir in 1 to 2 tablespoons (15 to 30 ml) of milk if it will not spread. Avoid coconut flakes that are very large, since they can make the layer harder to cut.
Keep the holes shallow enough. The holes should hold filling without going all the way through the cake. A wooden spoon handle makes wider pockets than a skewer, which helps the coconut mixture distribute through the crumb. If you only have a skewer, make more holes and spread the filling gently so the surface stays intact.
Let the ganache settle before pouring. Very hot ganache can melt the filling and mix into it. Let it cool briefly until it is still pourable but no longer piping hot. If it thickens too much, warm it for a few seconds at a time over gentle heat, stirring between intervals.

Serving Suggestions

Serve small squares chilled or let them sit at room temperature for 10 to 15 minutes before eating. The brief rest softens the ganache without making the coconut layer runny. Since the cake is rich, a 9-by-13-inch pan usually gives 12 generous portions; cut it into 15 or 16 smaller squares for a dessert table or after a substantial meal.

A few toasted coconut flakes on each piece make the coconut flavor clear and add a little crunch. Fresh strawberries or raspberries also work well alongside a slice, bringing a tart contrast to the sweet filling. For a simple plated dessert, serve the cake with a small scoop of vanilla ice cream or a spoonful of lightly sweetened whipped cream. Keep accompaniments separate until serving so the topping remains neat.

Variations

Use a different chocolate base: Dark chocolate cake mix makes the dessert less sweet-tasting and emphasizes the contrast with the coconut layer. Devil’s food mix gives a darker, softer crumb. Keep the same pan size and use the baking time on the box as your starting point, since mixes can vary slightly.

Add almond flavor: Replace the vanilla extract in the filling with 1/2 teaspoon (2.5 ml) almond extract, or use 1/2 teaspoon each of vanilla and almond. Almond extract is potent, so do not substitute it one-for-one unless you want a pronounced flavor. A small handful of sliced almonds scattered on top adds crunch, though it moves the flavor away from the classic coconut-and-chocolate pairing.

Make a lighter-tasting topping: Use 10 oz (285 g) semisweet chocolate with the same 1 1/2 cups (360 ml) cream for a softer, less chocolate-dense layer. It will be more delicate when sliced, so chill the cake thoroughly and use a warmed knife. For a sweeter finish, use milk chocolate, but expect a softer topping and a noticeably sweeter overall cake.

Make it in two layers: For a more formal presentation, bake the mix in two greased 8-inch (20-cm) round pans, following the box’s guidance for layer cakes. Cool completely, then spread the coconut filling between the layers and cover the top with ganache. This version is less convenient to transport and serve than the sheet cake, and the layers need to be fully cool before stacking.

Storage and Reheating

Because the filling and ganache contain dairy, refrigerate the cake within 2 hours of baking or serving. Cover the pan tightly or transfer slices to an airtight container; refrigerated, the cake keeps well for 3 to 4 days. The topping firms in the refrigerator, so for a softer texture, set individual portions out for 10 to 15 minutes before serving. Do not leave the cake at room temperature for more than 2 hours, or more than 1 hour in temperatures above 90°F (32°C).

This cake is best served cool or slightly softened rather than reheated. If you prefer a warmer slice, microwave one portion for about 5 seconds, then check it and repeat in 5-second intervals only if needed. Longer heating can make the filling too hot and cause the chocolate topping to melt. To freeze, wrap individual pieces well and freeze for up to 2 months; thaw them overnight in the refrigerator, still wrapped, to limit condensation on the ganache.

Frequently Asked Questions

Is this the same as a traditional Mounds cake?

There is no single fixed recipe for a Mounds-style cake. Versions commonly pair chocolate cake with coconut and a chocolate topping, but the cake, filling, and frosting vary. This cake-mix version uses a condensed-milk coconut layer and a simple chocolate ganache for an easy sheet-pan dessert.

Can I use a different size cake mix?

A mix close to 15.25 ounces (432 g) is the best fit for this recipe in a 9-by-13-inch pan. If your box is substantially smaller or larger, use its own directions and check the pan capacity before baking. A thinner batter layer may bake faster, while an overfilled pan can spill or leave the center underbaked.

Can I make the cake a day ahead?

Yes. Assemble and chill it, then cover the pan once the ganache has set and refrigerate overnight. The filling will have time to settle, and the cake will be easy to portion the next day. For the neatest surface, press plastic wrap onto the pan’s cover or use a lid that does not touch the topping.

Why is my coconut filling difficult to spread?

It may have too much coconut, or the coconut may be especially dry or densely packed. Stir in 1 tablespoon (15 ml) of milk at a time until the mixture is moist enough to spread, then add it to the cake while the cake is still warm. Spread with a light hand; the filling does not have to enter every hole to taste good.

Can I use frosting instead of ganache?

Yes. Use about 2 cups (320 g) of prepared chocolate frosting and spread it over the cake only after the cake has cooled completely. Frosting makes a sweeter, thicker top than the ganache in this recipe. If the cake is still warm, the frosting may soften and slide, so allow the full cooling time first.

How do I know when the cake is done?

Start checking at the earliest bake time on the cake-mix box. Insert a toothpick into the center, away from the edge of the pan; it should come out clean or with a few moist crumbs. If you see wet batter, bake for another 2 to 3 minutes and check again. Avoid repeatedly opening the oven early in the bake, since a sudden temperature drop can affect the cake’s rise.

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