1 1/4 cups
(175g) all-purpose flour
8 tablespoons
(1 stick, 113g) cold unsalted butter, cut into small squares
1 1/2 teaspoons
granulated sugar
1/2 teaspoon
fine sea salt
1/2 cup
(about 115g) ripe sourdough starter (liquid; 100% hydration)
3 tablespoons
cold water, plus more as needed
1 cup
(about 150g) blueberries
1 pound
ripe peaches (about 450g), sliced
1 tablespoon
freshly squeezed lemon juice
2 teaspoons
cornstarch
1/2 teaspoon
fine sea salt
1/4 cup
(50g) granulated sugar
1
egg, beaten
1 tablespoon
whole milk
1 handful
coarse sugar (for topping the crust before baking)