Save My sister called at 7 AM on a Sunday, asking if I could make something for her book club brunch that wouldn't require last-minute fussing. I had sourdough sitting on my counter and a container of blueberries that needed using, so I threw together this baked French toast casserole on instinct. What arrived at her place two hours later—golden, custardy, and smelling like cinnamon and buttered bread—became the dish people actually remembered from that morning.
I've made this at least a dozen times now, and the moment I knew it was permanent in my rotation was watching my neighbor take a bite at a potluck, close her eyes, and ask for the recipe before she'd even swallowed. She'd been skeptical about sourdough in dessert territory, but the slight tang against the sweetness converted her instantly.
Ingredients
- Sourdough bread: Use a day-old loaf for structure that holds the custard without turning to mush—fresh bread falls apart too quickly.
- Fresh or frozen blueberries: Both work beautifully; frozen ones keep their shape better and won't bleed color everywhere if you prefer that tidiness.
- Eggs: Six large ones create the custard body, so don't skimp or substitute with smaller eggs.
- Whole milk and heavy cream: This combination gives you richness without being heavy—use the exact ratio or it won't set properly.
- Granulated sugar: Sweetens the custard so it balances the bread's natural tang.
- Pure vanilla extract: The good stuff makes a noticeable difference here since it's a main flavor note.
- Ground cinnamon and nutmeg: Toast these spices briefly if you have whole ones—the warmth brings out their oils and complexity.
- Fine sea salt: Cuts through sweetness and makes every flavor pop, so don't omit it.
- Brown sugar and melted butter topping: Creates a light crust that keeps the inside custardy and the outside satisfying.
Instructions
- Prepare your vessel:
- Butter your baking dish thoroughly—the corners especially—so nothing sticks when you serve. Sourdough has enough texture that it won't slide around, but butter makes release effortless.
- Layer bread and berries:
- Scatter cubed sourdough evenly, then nestle blueberries throughout so you get fruit in every bite. Don't cluster them in one corner or you'll have a lopsided final dish.
- Make the custard:
- Whisk eggs, milk, cream, sugar, vanilla, cinnamon, nutmeg, and salt until the mixture is smooth and the sugar has dissolved—you want no gritty feel on your tongue when you test it. The color should be pale golden.
- Soak the bread:
- Pour custard slowly over bread and gently press down with the back of a spoon so it absorbs evenly without compacting. You want the bread slightly submerged but still holding its shape.
- Chill overnight:
- Cover and refrigerate for at least two hours, or better yet, overnight so the bread fully absorbs the custard and flavors meld. This step is non-negotiable if you want creamy insides.
- Add the topping:
- Mix melted butter, brown sugar, and cinnamon, then drizzle across the top just before baking so it doesn't sink and soften. This creates the texture contrast that makes each spoonful interesting.
- Bake until golden:
- At 350°F, this takes 40 to 45 minutes—you're looking for the center to barely jiggle when you shake the pan and the top to be caramel-brown. A knife inserted near the center should come out clean or with just a few custard crumbs.
- Rest before serving:
- Let it sit for 10 minutes so the custard sets slightly and becomes easier to portion without falling apart. This brief rest also lets the heat dissipate so your guests don't burn their mouths.
Save There's a moment when this dish comes out of the oven and the smell of cinnamon and caramelized sugar hits you that you realize this isn't just breakfast—it's the kind of thing that makes people linger at the table, asking for seconds while coffee gets cold. That's when food becomes memory.
Why Sourdough Works Better Here
The tanginess of sourdough prevents this dish from feeling one-note or cloying, the way it would with plain white bread or brioche. That subtle sour note cuts through the custard and blueberries, creating a complexity that keeps you reaching for another forkful instead of feeling full after two bites. It's the bread doing the heavy lifting on flavor.
Make-Ahead Magic
This is the dream casserole for feeding a crowd because you can assemble it the day before and slide it straight into the oven. I've made this at 6 AM while still in my pajamas, pulled it from the fridge where it's been waiting patiently, added the topping, and had golden brunch ready before my guests finished their coffee. The custard actually tastes better after sitting overnight because the flavors settle into the bread.
Flavor Variations and Swaps
While blueberries are perfect, I've stretched this recipe with raspberries, sliced peaches, and even diced apples, and each shift the whole dish slightly. A handful of chopped pecans or walnuts stirred into the brown sugar topping adds crunch that transforms the texture. If you're using different bread—brioche is richer, challah is sweeter, whole wheat brings nuttiness—taste a small piece and adjust the sugar in the custard so nothing feels out of balance.
- Brioche or challah creates a more decadent, tender crumb if you want luxury-level brunch.
- Pecans and walnuts mixed into the topping add textural interest and subtle earthiness.
- A splash of bourbon or brandy whiskey in the custard for adults only elevates it into something closer to dessert.
Save This is the recipe I make when I want to show up for people without showing up exhausted. Serve it warm with a drizzle of maple syrup, a dusting of powdered sugar, or just as is, and watch how something so simple becomes the main reason people remember your brunch.
Recipe FAQ
- → Can I use frozen blueberries in this dish?
Yes, frozen blueberries can be used directly without thawing before baking, preserving their shape and flavor.
- → What can I substitute for sourdough bread?
Brioche or challah provide a richer, softer texture that complements the custard similarly well.
- → Is it necessary to refrigerate before baking?
Chilling the mixture for at least 2 hours allows the bread to fully absorb the custard, enhancing texture and flavor.
- → How can I add extra crunch to the topping?
Sprinkling chopped pecans or walnuts over the cinnamon-butter topping before baking adds a delightful crunch.
- → What temperature and time are recommended for baking?
Bake uncovered at 350°F (175°C) for 40–45 minutes until the center is set and the top turns golden brown.
