Cut the butter into small cubes, then, in a stand mixer or using your hands, mix with the flour and salt until the mixture resembles meal. Add the sour cream and mix until a smooth dough forms, but do not knead it. The dough should be uniform in texture, with no streaks of butter. Cover the dough with cling film and refrigerate for 30 minutes to rest.

Preheat the oven to 350. Remove the dough and roll it out to the shape of the tart pan on a floured surface. Press the dough into a greased tart pan, then perforate with a fork, cover with aluminum foil and fill with pie weights, such as dried lentils or beans. Bake the crust for 30 minutes, then remove and cool.

While the crust is baking, make the filling. Heat the cream until hot, then remove from the heat. Render the fat from the bacon and crisp it lightly, then remove with a slotted spoon, cool, and chop coarsely. Scatter the bacon in the tart shell, then the cheese.

In a blender, puree the cream (it should be warm, but not hot enough to cook the egg) with the eggs, a pinch of nutmeg and the salt. Pour the cream mixture into the tart shell, then bake at 375 for 15 minutes or until cooked and lightly browned. Allow the quiche to cool for 5-10 minutes before cutting to help it set. The quiche can also be made a day or two ahead of time and gently reheated before serving. Serve with a salad of fresh watercress dressed with lemon and olive oil.