Roll out the dough: Turn the dough out on a lightly floured work surface. Roll the dough out into a 12-inch rectangle.
236 grams sourdough puff pastry
Cut out dough portions: Using a sharp pairing knife or pizza wheel, trim ½-inch off the edges of the dough, this will encourage the layers to separate and the pastry to rise. Divide the dough into nine 3 ½-inch squares. Place the unbaked dough on a parchment-lined baking sheet.
Prep: Preheat oven to 425 F. Refrigerate the dough for at least 30 minutes.
Egg wash: Brush the edges of the dough with egg wash. Try your best not to get the egg wash on the edges, this will adhere the layers to each other and prevent them from puffing up.
1 egg
Assemble the tarts: Whisk the cornstarch and cane sugar together. Sprinkle the center of each portion of dough with the sugar mixture.
50 grams cane sugar, 10 grams cornstarch
Position the fruits on the center of the unbaked tart shells.
200 grams mixed berries
Bake: Bake the tarts for 15 to 20 minutes, or until the pastries have puffed up and are golden brown in color. Transfer the baked tarts to a cooling rack and let them cool before glazing.
Make the glaze: Combine the sifted powdered sugar, water, and vanilla, using a spatula or whisk stir the mixture until thoroughly combined and smooth. Add water a teaspoon at a time if you’d like to thin out your glaze.
60 grams powdered sugar, 8 grams water
Serve and store: Drizzle the glaze over the tarts and enjoy. These tarts are best enjoyed once they have cooled. Store any leftovers in an airtight container at room temperature for up to 3 days.