Lemon Blueberry Sourdough Toast

My neighbor knocked on my kitchen door one Saturday morning with a bag of blueberries she'd picked the day before, still dusty from the farm. She mentioned offhand that she'd been craving French toast but wanted something less fussy than standing at the stove flipping individual slices. That afternoon, I started experimenting with sourdough and custard, letting the bright tang of lemon play against the sweetness of those berries. By the time the casserole came out of the oven golden and fragrant, she was already calling friends to come over. What began as a casual kitchen moment became the breakfast we now make every time someone needs comforting.

The first time I made this for my book club's Sunday brunch, I was nervous about the timing. I'd read that overnight soaking deepens the custard absorption, but I wasn't sure if I'd miscalculated. When I pulled it from the oven and watched the steam rise, the center jiggled just slightly, and I knew it was perfect. Three of the women asked for the recipe before they'd finished their first bites, and one admitted she'd been intimidated by baked French toast casseroles until that moment.

Ingredients

• Sourdough bread, cut into 1-inch cubes (1 loaf, about 400 g): The sourness balances the sweetness and holds up beautifully to soaking without turning to mush, unlike softer breads that can get mushy or fall apart.
• Fresh or frozen blueberries (1½ cups / 225 g): Frozen berries work just as well and burst with juice as they thaw in the oven, releasing pockets of brightness throughout the bake.
• Lemon zest (from 1 lemon): This is where the magic happens—the oils from the zest distribute flavor more evenly than juice alone, giving you brightness in every bite.
• Large eggs (6): They're the binder that transforms milk and cream into a silky custard that clings to every piece of bread.
• Whole milk (2 cups / 480 ml): The dairy base that creates richness without heaviness when combined with cream.
• Heavy cream (½ cup / 120 ml): This adds richness and helps the custard set properly; don't skip it or the center may not firm up as nicely.
• Granulated sugar (⅓ cup / 65 g): Sweetens the custard gently without overshadowing the lemon and sourdough notes.
• Pure vanilla extract (2 tsp): A flavor anchor that makes the custard taste more complex and sophisticated.
• Salt (¼ tsp): This tiny pinch heightens every other flavor and keeps the dish from tasting one-dimensional.
• Lemon juice (from 1 lemon): Fresh juice adds tang that complements the sourdough's natural sourness.
• Unsalted butter, melted (2 tbsp / 28 g): This creates a golden, crispy top when combined with the cinnamon sugar.
• Granulated sugar and ground cinnamon (2 tbsp sugar, ½ tsp cinnamon): The topping that caramelizes slightly and adds texture contrast.

Instructions

Set up your canvas:

Grease a 9x13-inch baking dish generously with butter or oil so nothing sticks when you turn it out later. Arrange the sourdough cubes in an even layer—don't pack them too tightly or the custard won't reach all the way through.

Build the layers:

Scatter blueberries and lemon zest over the bread, mixing them throughout rather than letting the berries sink to the bottom. This ensures every forkful gets the citrus brightness.

Make the custard:

Whisk eggs, milk, cream, sugar, vanilla, salt, and lemon juice in a large bowl until the mixture is completely smooth and the sugar has dissolved. You want no graininess or undissolved egg whites.

The soak:

Pour the custard over the bread and berries, then gently press down with a spatula so the bread absorbs the mixture evenly. Don't be rough or you'll break apart the sourdough cubes.

Chill and wait:

Cover the dish and refrigerate for at least 30 minutes, though overnight is ideal. This waiting period is when the bread slowly drinks in the custard, which is what makes the final texture so tender.

Finish the top:

After preheating the oven to 350°F, drizzle melted butter over the surface and sprinkle the cinnamon sugar mixture evenly across. This creates a slightly crispy, caramelized top.

Bake until golden:

Bake uncovered for about 45 minutes until the center is just set (it will jiggle ever so slightly when you gently shake the dish) and the top is golden brown. Overbaking dries it out, so watch the timing.

Rest and serve:

Let it cool for 10 minutes so it sets enough to cut cleanly and serve warm. The brief rest also allows the flavors to meld beautifully.

Save to Pins

Last spring, my sister came home from a difficult week at work, and I made this casserole without asking if she wanted breakfast. We sat on the back porch with warm plates and strong coffee, and she didn't say much at first—just ate. Then she asked for seconds and finally smiled for the first time in days. That's when I realized food's quiet power: sometimes the most nourishing thing isn't the conversation, but the care that fills every corner of the plate.

Why Overnight Soaking Matters

The magic of this casserole lives in the hours between assembly and baking. When you refrigerate overnight, the sourdough gradually absorbs the custard, becoming tender but not soggy—it's a delicate balance that happens slowly. By morning, the bread has transformed into something custard-like in texture while retaining its structure, so each bite is creamy and soft without falling apart.

Lemon and Blueberry: A Partnership

The pairing of lemon and blueberry isn't trendy—it's timeless because the tartness of lemon makes blueberries taste more intensely blueberry-like. The citrus cuts through the richness of the custard and butter, keeping the whole dish feeling bright rather than heavy. This is why the zest matters so much; it's distributed throughout instead of settling to the bottom like juice would.

Make It Your Own

I've found that this recipe is forgiving enough to adapt but structured enough not to fall apart. Some mornings I substitute blackberries or raspberries when blueberries aren't at their peak, and the tartness shifts slightly but the technique remains the same. The framework of sourdough, custard, and citrus is what matters; everything else is personal preference and what's growing nearby.

• Raspberries or blackberries work beautifully if you want to shift the flavor profile slightly without changing the method.
• A dairy-free version using oat or almond milk and plant-based cream will bake a bit differently, so watch it closely and test the center earlier.
• Try a dusting of cardamom or nutmeg alongside the cinnamon for warmth and complexity.

Save to Pins

This casserole has become my answer to every question about what to make when people I care about are gathering around the table. It's humble enough not to feel showy, but comforting enough to say everything that matters.

Questions & Answers

→ What type of bread works best for this dish?

Sourdough bread is ideal as its sturdy texture absorbs the custard without becoming soggy, adding a tangy depth to the flavor.

→ Can frozen blueberries be used instead of fresh?

Yes, frozen blueberries work well and provide a burst of juicy sweetness when baked, though fresh berries offer a slightly firmer texture.

→ How long should the custard soak before baking?

Refrigerating for at least 30 minutes allows the sourdough to absorb custard fully, but soaking overnight yields more intense flavor and texture.

→ What variations can enhance the flavor?

Adding raspberries or blackberries alongside blueberries adds tartness, while a sprinkle of cinnamon and sugar creates a caramelized topping during baking.

→ Is there a way to make this suitable for dairy-free diets?

Substitute whole milk and cream with plant-based alternatives like almond or oat milk to maintain creaminess without dairy.