1. For the pastry, pulse the flour, sugar, and zest in a food processor. Add the butter and pulse until the mixture resembles bread crumbs. Add the egg and pulse until the dough begins to clump together. Chill for 30 minutes. Roll out on a floured work surface into a round about 1/8 in (3mm) thick. Line a 9in (23cm) tart pan with a removable bottom, and trim the excess. Refrigerate for 30 minutes.

2. Preheat the oven to 375°F (190°C). Line the pan with a round of wax paper and fill with baking beans. Bake about 12 minutes until the pastry looks set and begins to brown. Remove the paper and beans and bake 10 more minutes, until the pastry is lightly browned. Cool on a wire rack.

3. Reduce the temperature to 325°F (170°C). Mix the mascarpone, sugar, egg and yolk, milk, and vanilla together until smooth and pour into the tart shell. Arrange the sliced pears in the filling, sprinkle with the hazelnuts, and then the sugar. Bake for 30 minutes or until the filling is just set.

4. Cool on a wire rack. Brush with the preserves, slice, and serve.