Overnight Sourdough French Toast Bake (Make-Ahead Brunch)

This recipe was born out of a pile of bread crusts I refused to throw away. Cube them up, soak them overnight in a rich cinnamon custard, top with a brown sugar streusel, and you've got a breakfast that tastes like you woke up early and tried really hard. You did not. You made it the night before.

The sourdough discard in the custard is a small addition that makes a real difference. It adds a subtle tang that plays against the cinnamon and vanilla in the best way, and it's a smart use of discard that would otherwise go to waste. My kids and my husband go crazy over this one, hope you enjoy as much as we do!

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What You Need

For the casserole:

• 4 large eggs (200g)
• ¾ cup whole milk (180g)
• ¼ cup heavy cream (60g)
• 2 tablespoons sourdough discard (30g)
• 3 tablespoons organic cane sugar (36g)
• 1 teaspoon vanilla (4g)
• 1 teaspoon cinnamon (3g)
• ¼ teaspoon salt

For the bread:

• Crusts from Little Sealed Sandwiches, or roughly 3–4 cups day-old sourdough sandwich bread, cubed (120–160g)

For the streusel:

• ¼ cup all-purpose flour (30g)
• ¼ cup packed brown sugar (50g)
• ½ teaspoon cinnamon (1.5g)
• ¼ teaspoon salt
• 3 tablespoons cold unsalted butter, cubed (42g)

Equipment:

• 8x8 baking dish
• Large mixing bowl
• Whisk
• Small bowl for streusel
• Plastic wrap

Step-by-Step Instructions

Part 1: Assemble the Night Before

Step 1: Prep your bread

Grease your 8x8 baking dish. Arrange the bread cubes in an even layer in the pan. Day-old bread works best here because it absorbs the custard without getting too soggy. If your bread is fresh, spread the cubes on a baking sheet and let them sit out for a few hours to dry out a little. My kids have been living crustless sandwiches so I save all those crust for this morning treat.

Step 2: Make the custard

In a large bowl, whisk together the eggs, whole milk, heavy cream, sourdough discard, sugar, vanilla, cinnamon, and salt until fully combined. Pour it evenly over the bread. Press the bread down gently so every piece gets into the custard. Don't rush this step. You want it all soaked through.

Step 3: Refrigerate overnight

Cover tightly with plastic wrap and refrigerate for at least 6 hours, or overnight. This is where the magic happens. The bread absorbs everything and by morning you've got a fully loaded casserole ready to go straight into the oven.

Part 2: Streusel and Bake

Step 4: Make the streusel

When you're ready to bake, preheat your oven to 350°F. In a small bowl, combine the flour, brown sugar, cinnamon, and salt. Add the cold cubed butter and use your fingers to work it in until the mixture looks like coarse, crumbly sand with some pea-sized pieces in there. That's exactly what you want.

Step 5: Top and bake

Sprinkle the streusel evenly over the soaked bread. Bake uncovered for 35–40 minutes until the top is golden and the center is set. A knife inserted in the center should come out clean. If the streusel is browning too fast before the center sets, tent it loosely with foil.

Step 6: Cool completely

Let it cool slightly before slicing. I know it smells incredible. But the custard needs time to set, and cutting in too early gives you a soggy slices. We love drizzling with some maple syrup or eat just as is!

Storage Tips

Freezer: Once fully cooled, this actually holds up well in the freezer. Slice and flash freeze on a parchment-lined baking sheet for one hour, then transfer to a freezer-safe bag with a small square of parchment between each piece. Label with the date. Best within 3 months, use within 12 months.

Refrigerator: Store leftovers in an airtight container for up to 4 days.

Reheating: Microwave individual portions for 60–90 seconds, or warm in a 350°F oven or toaster oven for 8–10 minutes. The oven brings the streusel back to life better than the microwave if you have the extra few minutes.

Troubleshooting Tips

The center is still jiggly after baking. Give it 5 more minutes. Every oven runs a little differently. The center should feel set, not liquid, when you press it gently.

The streusel burned before the center was done. Your oven runs hot. Tent loosely with foil around the 20-minute mark next time, or drop the temperature to 325°F and bake a little longer.

The bread is soggy even after baking. It likely needed more time in the oven, or the bread was too fresh when you assembled it. Day-old or slightly dried-out bread absorbs the custard without turning to mush.

Final Thoughts

This one has become a regular in our house, especially on weekends when I want something that feels special without a lot of morning effort. The streusel on top, the cinnamon custard, the sourdough tang underneath. This all comes together really well.

If you make it, please tag me. I genuinely love seeing your kitchen wins.