- 1
Place the ricotta in a fine sieve for at least 20 minutes if it looks wet. A drier ricotta gives a creamier filling and prevents the base from becoming soggy.
- 2
Preheat the oven to 180°C / 356°F. Line a 22 cm / 8.7 in springform pan with baking paper, covering the base and lightly greasing the sides.
- 3
In a large bowl, mix the flour, sugar, baking powder, salt, and lemon zest. Stir well so the baking powder is evenly distributed.
- 4
Add the cold cubed butter. Rub it into the flour with your fingertips until the mixture looks like coarse sand with small buttery crumbs.
- 5
Add the egg and vanilla extract. Mix with your fingertips or a fork until the dough forms moist crumbs. Do not knead into a smooth dough; the texture must stay crumbly.
- 6
Place about two-thirds of the crumble mixture into the prepared pan. Press it gently over the base and slightly up the sides to create a rustic shell.
- 7
In another bowl, combine ricotta, powdered sugar, egg yolk, vanilla, and lemon zest. Mix until smooth and creamy. Fold in the chocolate chips if using.
- 8
Spoon the ricotta filling over the crumble base and spread it evenly with a spatula, leaving the surface smooth but not compressed.
- 9
Scatter the remaining crumble mixture over the ricotta filling, covering it evenly. Leave some irregular crumbs visible for a rustic golden finish.
- 10
Bake for 35 to 40 minutes, or until the top is lightly golden and the edges are firm. The center should look set but still soft.
- 11
Let the tart cool completely in the pan before removing it. For the cleanest slices, chill it for 1 hour before serving.
- 12
Dust with powdered sugar just before serving and slice with a sharp knife.