Step 1

Roll-out dough: Roll out dough on a clean, lightly floured surface into a 12-inch circle. Line a 10 by 1 1/2-inch tart pan with the rolled out dough. Trim the edges.Chill in freezer for 30 minutes. (You need to pre-freeze the raw crust or it will slip down the sides of the pan when it cooks.)At this point, if you are using a pre-frozen pie crust proceed to step 2.

Step 2

Pre-bake crust: Preheat oven to 350°F. Line the crust with aluminum foil or parchment paper, pushing into the bottom edge. Don't cut the foil or parchment paper too close to the crust, allow for enough room to easily lift it out.Fill it at least two-thirds with baking weights—dried beans (I keep a bag of pinto beans just to use for pie weights), rice, or aluminum pie weights. Bake initially for 15 minutes, then remove from oven and let cool a few minutes. Carefully remove parchment paper and weights.Poke the bottom of the pie pan with the tines of a fork and return to oven and bake an additional 10 minutes or until lightly golden. (Fork holes are for any air to escape.) Let cool on a rack while you make the filling.

Step 3

Sauté shallots and mushrooms: Heat oil in a large nonstick skillet over medium high heat. Sauté the shallots for a minute, then add the mushrooms.Sprinkle with salt and pepper and cook, stirring frequently, until the mushrooms release all of their moisture, and get well browned, about 10 minutes.

Step 4

Make the egg cream milk filling: Whisk together the cream, milk, and eggs in a medium bowl. Stir in nutmeg, salt and pepper.

Step 5

Assemble the tart: Place the tart pan on a rimmed baking sheet to catch any run-off or leaks. Sprinkle half of the grated Gruyere over the bottom of the crust. Spread the mushrooms and shallots over the cheese in an even layer, and sprinkle with the remaining cheese. Pour the egg mixture over the mushrooms and cheese in the crust.

Step 6

Bake: Put the baking sheet with the tart pan in the oven and bake at 350°F until the center is just set, still a little wiggly, about 30 to 35 minutes.Remove to a rack and let cool for 20 minutes before slicing.