Makes 1 9-inch tart or several smaller tarts

Prepare crust: Combine butter, flour and salt in food processor. Process until mixture looks like corn meal – a few little lumps of butter are OK. Add ice water a few drops at a time while processing, just until mixture starts to come together. Turn dough onto large piece of plastic wrap, gather together and form a flat round and refrigerate for one hour. Roll out to 3/8” thick to fill tart pan or pans. Press extra dough into pan sides to make thicker. Refrigerate while preparing filling.

Slice best-looking mushrooms into ¼” slices. (Save unused scraps for another dish) Heat oil in large sauté pan and add mushrooms, being careful not to break them. Add salt and pepper and cook over moderately high heat until golden brown. Carefully remove to a dish. In same pan, adding a teaspoon of oil if necessary, cook leeks for a few minutes, being careful not to separate the rings. Set aside. In a large bowl, whisk together crème fraîche, half-and-half, eggs and pepper until well blended. Transfer to a container with a spout.

Preheat oven to 375 degrees. Prick unbaked crusts all over with a fork and bake for 20-25 minutes, until pale golden. Lower heat to 350 degrees. Sprinkle cheese cubes in crust, then carefully pour in filling. Bake for 20-25 minutes, until filling is barely set but still wobbly. Remove from oven and arrange dill fronds, mushrooms and leeks decoratively on top of quiche. Return to oven for 10-15 more minutes, or until filling is set and crust is pale golden. Remove and cool slightly. Serve warm or room temperature. Store in refrigerator.