Mix Dry Ingredients: Add the all-purpose flour, almond flour, powdered sugar, and salt to a food processor. Pulse a couple of times just to combine the dry ingredients evenly.
1 cup all-purpose flour, 3 tablespoons almond flour, ½ cup powdered sugar, ⅛ teaspoon salt
Cut In Butter: Add the cold, cubed unsalted butter and pulse a few times until the mixture looks sandy and you can see tiny specks of butter throughout.
4 ½ tablespoons unsalted butter
Add The Egg: Pour in the whisked egg and pulse a few times until the dough looks roughly combined. It should still be uneven and crumbly at this stage.
½ large egg
Finish Dough By Hand: Transfer the mixture to a bowl or a clean work surface and quickly press it together by hand until it forms a dough. Work fast so the butter stays cold.
Chill The Dough: Wrap the dough in plastic wrap or place it in a plastic bag and flatten slightly into a disk so it chills faster and hydrates evenly. Refrigerate for at least 1 hour, or ideally overnight.
Roll And Chill: Roll the dough out to about 3 mm thickness on lightly floured parchment paper or a silicone mat. Turn the dough every couple of passes and add a little flour if it starts sticking. Use you hands as little as possible so it doesn't warm up. Once rolled, freeze for 15 to 30 minutes until slightly firm but still flexible.
Transfer To Pan: Lightly butter your tart pan or pie dish if it isn’t non-stick, then place the chilled dough over the pan.
Press Into Pan: As the dough warms slightly, gently press it into the bottom and sides of the pan. Make sure it fits into all the corners, especially where the base meets the sides.
Trim And Dock: Trim the excess dough by pressing a sharp knife from the inside of the pan outward. Press the edges again so the dough sticks well to the pan, then prick the bottom with a fork to dock.
Freeze Before Baking: Freeze the shaped tart shell for about 30 minutes to help the crust hold its shape during baking.
Bake The Shell: Bake at 180°C (355°F) for 15–18 minutes, or until the edges are lightly golden.
Cool Before Filling: Let the tart shell cool completely in the pan before adding any fillings.