Prep the apples – Peel, core, and dice your apples into small, even pieces. Toss them with lemon juice, brown sugar, cinnamon, nutmeg, and vanilla extract. Set aside.

Preheat the oven – Crank it up to 400°F (200°C). You want a hot oven so the pastry gets crispy and golden.

Roll out puff pastry – Lightly flour your surface and roll out the sheet. Cut it into small squares, about 3x3 inches each.

Assemble the tarts – Spoon a little apple mixture into the center of each square. Fold edges slightly to create a mini border, leaving the filling visible.

Brush with egg wash – Beat the egg and brush it over the edges of each tart. This is what gives your tarts that bakery-glossy finish.

Bake – Pop them into the oven for 18-22 minutes, or until the pastry is puffed and golden brown. The apples should be bubbling slightly.

Cool & enjoy – Let them cool a few minutes on a wire rack. Or…eat one immediately. We won’t tell.