1. Preheat the oven to 400°F (200°). Make the pastry: Sift the flour and salt into a large bowl. Add the butter and cut into the flour with a pastry blender until it resembles coarse bread crumbs. Stir in enough water to make a firm dough. Wrap and chill for 30 minutes. Roll out on a floured work surface into an 1/8 in (3mm) thick round. Line the tart pan with the pastry and trim any excess. Refrigerate for 30 minutes.

2. Put the pan on a baking sheet. Line the tart shell with parchment paper, fill with baking beans, and bake 15 minutes, until the dough looks set. Remove the paper and beans and bake another 5 minutes, until the pastry starts to brown. Transfer to a wire rack to cool. Reduce the oven to 350°F (180°C).

3. Meanwhile, melt the butter in a frying pan over medium-low heat. Add the onion and cover. Cook, stirring, for 10 minutes, until tender. Add the bacon and increase the heat to medium-high. Cook, uncovered, stirring, about 5 minutes.

4. Meanwhile, mix the ricotta, eggs, and milk. Stir in the Parmesan, chives, and thyme. Season with salt and pepper. Stir in the bacon and onion and pour into the pastry shell. Bake for 35 minutes or until the filling has set. Let cool in the pan. Transfer to a serving platter and serve.