Sourdough Chestnut Caramel Tarts

What Makes This Special

The crust is leavened with sourdough starter, which creates a faintly tangy, flaky pastry uncommon in French tart shells. Chestnut puree and caramelization add structure, autumnal aroma, and a rustic visual. The tart format is suited for transport and serving.

Ingredients

Sourdough starter functions as both acid and leaven. Chestnut puree is dense and requires fat and egg for lift. Sugar caramelizes for depth. Apples add acidity and moisture.

For the Sourdough Tart Shell

• 120g active sourdough starter (100% hydration)
• 200g plain flour
• 40g whole wheat flour
• 6g fine sea salt
• 40g unsalted butter, cold, cubed
• 30g sugar
• 50g cold water

For the Chestnut Caramel Frangipane

• 100g unsalted butter, room temperature
• 80g caster sugar
• 30g light brown sugar (for caramelization)
• 100g chestnut puree
• 80g ground almonds
• 2 large eggs
• 2ml vanilla extract
• 1 pinch salt

For the Caramelized Apples

• 2 medium tart apples, cored, thinly sliced
• 10g unsalted butter
• 10g sugar

Optional Garnish

• Toasted chestnut pieces

Instructions

Step 1: Make and Ferment Sourdough Tart Dough

Combine flours, salt, and sugar in a bowl. Add cold butter and rub or cut in until mixture has small, visible butter pieces. Add sourdough starter and water. Mix just until dough forms. Do not knead. The butter must remain in small pieces for flakiness. Flatten dough into a disc, wrap, and refrigerate 1 hour. This rest chills butter and hydrates flour.

After resting, remove from fridge. Roll out to 3mm thick. Cut and line tart pans, trimming excess. Dock bases with a fork. Cover, then proof at 23–25°C until dough has risen slightly and feels puffy, 4–5 hours. Sourdough fermentation is slow in the fridge; room temperature is required for rise. The dough will not double, but if under-fermented, the crust will be tough.

Step 2: Blind Bake the Shells

Preheat oven to 180°C. Freeze lined tart shells for 15 minutes. This prevents shrinkage. Line each with parchment, fill with weights/beans. Bake 13 minutes. Remove weights and bake 5 minutes more. Shells should be firm and just beginning to color. Cool completely. Blind baking prevents a soggy bottom when filling is added.

Step 3: Caramelize Chestnut Frangipane Sugar

Melt 30g light brown sugar in a small pan over medium heat until deep amber. Watch closely. Remove from heat and immediately whisk in 20g of the butter for the frangipane (from the 100g total). Cool to room temperature. Caramelization creates Maillard compounds and autumnal aroma.

Step 4: Make Chestnut Frangipane

Cream remaining 80g butter and 80g caster sugar until pale and fluffy. Beat in eggs one at a time. Add vanilla, pinch of salt, chestnut puree, and ground almonds. Mix until homogenous. Fold in cooled caramel-butter mixture. The emulsion must not break: use room temperature ingredients. Caramel adds depth and a sticky texture.

Step 5: Caramelize Apples

Melt 10g butter in a pan. Add apple slices and 10g sugar. Cook over medium heat, stirring, until apples are pliable, glossy, and edges are caramelized, about 5 minutes. Do not overcook; they must hold shape. Set aside to cool.

Step 6: Assemble and Bake

Preheat oven to 175°C. Spoon frangipane into tart shells, smoothing with a spatula. Arrange caramelized apple slices on top. Bake 20–22 minutes (mini tarts), or 30–33 minutes (large tart), until filling is puffed and light golden. Cool in pans 10 minutes, then unmold and finish cooling on a wire rack. Top with optional chestnut pieces.

Pro Tips

• Active sourdough starter is mandatory. If sluggish, the crust will be dense and lose flakiness.
• Blind baking is not optional; unbaked shells will go soggy from frangipane moisture.
• Caramel must be taken off the heat before it smokes. Burnt sugar will overpower.

Troubleshooting

Shell is hard or tough? Likely under-fermented or overworked. Next time, ensure proof is at a warm room temperature and handle dough minimally.

Frangipane greasy or separated? Butter or caramel was too warm, or eggs too cold. All ingredients should be at room temperature before mixing.

Apples soggy or collapse? Overcooked. Cook until just translucent.

Variations

• Replace apples with firm pears; adjust caramelization time as pears soften faster.
• Add 15g cocoa to the frangipane for a chocolate-chestnut version.
• Use hazelnut meal instead of almonds for a different nut profile.

Storage

Store tarts in an airtight container at room temperature up to 18 hours. For longer, refrigerate up to 3 days, returning to room temperature to serve. The crust will soften in the fridge but remain edible.