This French toast casserole with Karo syrup is a make-ahead breakfast bake that turns humble bread and eggs into a golden, custardy, pull-apart dish. The Karo syrup (light corn syrup) creates a sweet, glossy topping that caramelizes as it bakes, while the bread soaks up a rich cinnamon-egg mixture overnight. It’s the perfect centerpiece for a holiday morning or a lazy weekend brunch, serving a crowd with minimal fuss.
Ingredients
- 1 large loaf (about 16 oz / 450 g) brioche or challah bread, cut into 1-inch cubes
- 8 large eggs
- 2 cups (480 ml) whole milk
- 1/2 cup (120 ml) heavy cream
- 3/4 cup (150 g) granulated sugar
- 1 tablespoon vanilla extract
- 1 teaspoon ground cinnamon
- 1/4 teaspoon ground nutmeg
- 1/2 teaspoon salt
- For the topping:
- 1 cup (240 ml) Karo light corn syrup
- 1/2 cup (115 g) unsalted butter, melted
- 1 cup (200 g) packed brown sugar
- 1 teaspoon vanilla extract
- Optional: 1 cup (120 g) chopped pecans or walnuts
Instructions
- Lightly grease a 9×13-inch (23×33 cm) baking dish. Place the bread cubes in the dish, spreading them evenly.
- In a large bowl, whisk together the eggs, milk, heavy cream, granulated sugar, vanilla, cinnamon, nutmeg, and salt until the sugar is dissolved and the mixture is smooth.
- Pour the egg mixture evenly over the bread cubes. Press the bread down gently with a spatula to help it absorb the liquid. Cover the dish with plastic wrap and refrigerate for at least 8 hours, or overnight.
- When ready to bake, preheat the oven to 350°F (175°C). Remove the casserole from the refrigerator and let it sit at room temperature for 20-30 minutes while the oven heats.
- In a small bowl, stir together the Karo syrup, melted butter, brown sugar, and vanilla. If using nuts, fold them in. Pour this mixture evenly over the top of the casserole.
- Bake uncovered for 40-45 minutes, until the top is golden and puffed, and the center is set. To check doneness, insert a knife near the center; it should come out clean. The internal temperature of the egg custard should reach 160°F (71°C) as a safe minimum, per USDA FSIS guidelines. Use a food thermometer to verify.
- Let the casserole rest for 5-10 minutes before serving. It will firm up as it cools slightly.
Tips
- Use stale bread: Slightly stale or day-old bread absorbs the custard better without becoming mushy. If your bread is fresh, you can toast the cubes in a 300°F (150°C) oven for 10 minutes before assembling.
- Don’t skip the overnight soak: The long soak allows the bread to fully absorb the custard, resulting in a creamy interior. If you’re short on time, a minimum of 4 hours will work, but 8 hours is best.
- Cover if browning too fast: If the top gets too dark during baking, loosely cover the casserole with aluminum foil for the last 15 minutes.
- Substitute the syrup: If you don’t have Karo, you can use light corn syrup or a mix of honey and maple syrup, though the flavor and texture will change slightly. Karo prevents crystallization and gives a glossy finish.
Serving Suggestions
Serve this casserole warm, straight from the dish, with a dusting of powdered sugar and a drizzle of extra maple syrup if desired. It pairs beautifully with fresh berries, sliced bananas, or a dollop of whipped cream. For a savory contrast, add crispy bacon or breakfast sausage on the side. A pitcher of freshly squeezed orange juice or a pot of coffee completes the brunch spread.
Variations
- Berry Bliss: Fold 1 cup (150 g) of fresh blueberries or raspberries into the bread cubes before adding the custard.
- Apple Cinnamon: Sauté 2 peeled, chopped apples with 1 tablespoon butter and 1 teaspoon cinnamon until soft, then layer them with the bread cubes.
- Chocolate Hazelnut: Spread a thin layer of chocolate-hazelnut spread between the bread slices before cubing, or add 1/2 cup (85 g) of chocolate chips to the casserole.
- Vegan Option: Use a plant-based milk (like oat or almond) and a vegan egg substitute (such as flax eggs) for the custard, and substitute the butter with vegan butter. Note that the texture will be softer and less rich.
Storage and Reheating
Store any leftover casserole in an airtight container in the refrigerator for up to 4 days. To reheat, place individual portions in the microwave for 1-2 minutes, or reheat the whole casserole in a 350°F (175°C) oven for 15-20 minutes, covered with foil to prevent drying. You can also freeze the baked casserole for up to 2 months; thaw overnight in the fridge and reheat as directed.
Frequently Asked Questions
Can I make this casserole without an overnight soak?
Yes, but the texture will be less custardy. A minimum of 2 hours is needed for the bread to absorb some liquid, but for the best results, aim for 8 hours or overnight.
Can I use regular sandwich bread instead of brioche?
Yes, but the casserole will be less rich and may turn out slightly drier. If using sandwich bread, use a sturdy variety and don’t over-soak it.
Why did my casserole turn out soggy?
Sogginess usually happens when the bread hasn’t absorbed the custard evenly, or if you used too much liquid for the amount of bread. Press the bread down gently after pouring the custard, and make sure your bread is stale or toasted.
Can I use dark corn syrup instead of Karo light?
Yes, but dark corn syrup has a stronger, more molasses-like flavor and will make the topping darker and less sweet. It will still work, but the taste will be different.
Is it safe to leave the casserole out while baking?
No, always refrigerate the unbaked casserole until you are ready to bake. Never leave it at room temperature for more than 2 hours total, including prep time.
How do I know when the casserole is done?
The top should be golden brown and puffed, and a knife inserted into the center should come out clean. The internal temperature should be at least 160°F (71°C) to ensure the eggs are fully cooked.
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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