Sourdough Egg Tarts Recipe: Flaky Crust and Runny Yolk Magic

This sourdough egg tart recipe delivers the perfect balance of flaky crust and runny yolk magic that makes every bite irresistible. 💛 The secret lies in using a well-fermented sourdough starter for a tangy, airy crust that contrasts beautifully with the creamy egg custard filling.

I've perfected this technique through countless trials, ensuring the crust stays crisp while the custard remains silky and golden at the center.

The beauty of this recipe is its versatility—whether you're baking traditional Hong Kong-style egg tarts or experimenting with gluten-free crusts, the principles remain the same. The key steps include preparing the sourdough starter, assembling the tart shells, and baking them just until golden before filling with the custard mixture.

This method ensures a flaky, buttery crust that holds up perfectly to the rich, custardy filling.

What you'll achieve is a batch of egg tarts with a golden, crispy crust that encases a velvety custard center, still runny in the middle for that classic egg tart experience.

The aroma alone will have everyone gathering around the kitchen, and the first bite delivers that perfect harmony of textures and flavors. These tarts are ideal for breakfast, brunch, or even as a delightful dessert.

Serve them warm with a dusting of powdered sugar or a drizzle of honey for an extra touch of sweetness. The recipe scales easily, so you can make a small batch for personal enjoyment or a larger batch for sharing with friends and family.

Let's get started on creating these delicious treats!

Ingredients for sourdough egg tart

Six ingredients transform sourdough into golden, crisp crusts and velvety custard centers.

The sourdough starter is non-negotiable here—it's what gives these tarts their signature tang and airy texture. King Arthur or Bob's Red Mill flours work best for the crust, but any high-protein all-purpose will do. For the butter, European-style (like Plugrá) has more fat content, which translates to flakier layers. If your starter isn't active, feed it 1:1:1 (flour:water:starter) by weight 4-6 hours before using. The eggs should be room temperature—cold eggs make the custard grainy. For the milk, whole is ideal, but 2% works in a pinch if that's what you have.

No sourdough starter? Instant yeast (1/4 tsp) can substitute, but the flavor won't be the same. For the butter, vegetable shortening gives a similar flaky texture if you're avoiding dairy. The vanilla extract can be swapped for 1/4 tsp vanilla bean paste if you want extra depth. If you're making these gluten-free, King Arthur GF flour blend works well—just increase the butter by 1 tbsp. For the custard, if you're concerned about it being too runny, add 1 extra tbsp cornstarch. The powdered sugar is just for dusting—skip it if you're serving these as a savory tart (yes, they work for that too!).

The sourdough starter keeps in the fridge for 1 week—feed it weekly to maintain activity. Store the flour and sugar in airtight containers for 6 months, while the butter should be used within 3 months of opening. The custard mixture can be made a day ahead and stored in the fridge—bring it to room temperature before using. For the finished tarts, they're best eaten warm but can be reheated in a 350°F oven for 5-7 minutes to restore crispness. Freeze unbaked tart shells for 1 month—just bake straight from frozen, adding 2-3 extra minutes.

Step-by-step instructions for sourdough egg tarts

Master this classic with a perfectly flaky crust and custard that stays runny at the center.

In a large mixing bowl, combine the 0.5 cup sourdough starter with the 2 cups all-purpose flour and 0.5 tsp salt. Mix until fully incorporated, then cut in the 0.5 cup cold, cubed unsalted butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs with pea-sized butter pieces.

Add the 0.25 cup granulated sugar and mix again. Gradually add 3 tablespoons of ice water (not listed in ingredients—this is your secret) while mixing until the dough just comes together. The dough should be slightly shaggy but hold when pressed. Wrap in plastic wrap and chill for 30 minutes to firm up.

Preheat your oven to 375°F. On a lightly floured surface, roll out the chilled dough to about ⅛-inch thickness. Cut into six 3-inch rounds using a round cutter or glass. Press each round into a greased mini tart pan or muffin tin, creating a slight rim.

Bake for 12-15 minutes until the edges are light golden brown and the crusts feel firm to the touch. Remove from oven and immediately prick the bottoms with a fork to prevent puffing. Return to oven for 2-3 more minutes to finish drying. Let cool for 5 minutes before filling.

In a medium saucepan, whisk together the 3 whole large eggs, 0.5 cup milk, 0.5 cup sourdough starter (yes, again—this adds tangy depth), 0.5 tsp vanilla extract, and 1 tbsp cornstarch. Cook over medium-low heat, stirring constantly with a silicone spatula, until the mixture thickens enough to coat the back of a spoon (3-5 minutes).

Remove from heat and stir in the 1 tbsp honey for subtle sweetness. The custard should be thick but still pourable. Let it cool slightly to body temperature—this prevents scrambled eggs when poured into hot crusts.

Fill each cooled tart shell with about 2 tablespoons of custard mixture. The custard should come about ½-inch from the top edge. Bake at 350°F for 18-20 minutes until the edges are set but the centers remain slightly jiggly—this ensures that runny yolk you crave.

Remove from oven and immediately dust the tops with 2 tbsp powdered sugar using a fine-mesh sieve. Let cool for 5 minutes before serving to allow the custard to set slightly while keeping that signature gooey center.

Dietary considerations for this dish

Gluten-Free Adaptation

For a gluten-free version, replace the all-purpose flour with King Arthur gluten-free flour blend (about 2 cups). Increase the cold butter by 1 tablespoon to compensate for the blend's lower protein content.

The sourdough starter remains key—it adds tang without gluten. Chill the dough 10 minutes extra since gluten-free dough behaves differently. 💛

Dairy-Free Options

Swap the unsalted butter for vegetable shortening (like Crisco) or coconut oil (solid, not melted) to maintain flakiness. Use unsweetened almond milk instead of whole milk in the custard, and add ½ teaspoon xanthan gum to the flour blend for structure.

The custard will still be creamy but slightly lighter in texture.

Lower Sugar Version

Reduce the granulated sugar in the crust to 2 tablespoons and omit the honey in the custard. Use 1 teaspoon monk fruit sweetener instead for zero glycemic impact.

The sourdough starter’s natural tang balances the reduced sweetness beautifully. For extra richness, add 1 tablespoon tahini to the custard—it adds depth without sugar.

Nut-Free Considerations

If avoiding nuts entirely, skip the almond milk substitution in the custard and stick with lactose-free milk (or oat milk for a neutral flavor). Ensure your King Arthur gluten-free blend is certified nut-free.

Always check labels on vanilla extract—some brands process in nut facilities. The crust remains nut-free as long as you use a dedicated rolling surface.

Egg-Free Substitutes

Replace the 3 eggs with 3 tablespoons aquafaba (chickpea brine) for each egg, whipped to stiff peaks. Add ½ teaspoon cream of tartar to stabilize the custard. For binding, include 1 tablespoon ground flaxseed mixed with 3 tablespoons water (let sit for 5 minutes).

The texture will be slightly denser but still custard-like. Bake the tarts 2 minutes longer to ensure the filling sets properly.

Frequently asked questions