For the crust: Preheat the oven to 375 degrees F. Pulse
together the flour and salt in a food processor
. Add the chilled butter and pulse just until the butter is evenly distributed throughout. Add the sour cream
and continue to pulse 2 to 4 more times until just incorporated. Add 2 tablespoons of ice water at a time, pulsing after each addition, until the dough starts to hold together. Add more water as needed.
Turn the dough out onto plastic wrap
and form it into a disc. Wrap the dough in the plastic wrap and let rest in the refrigerator 30 minutes.
Roll the dough on a floured surface into a 12-inch circle about 1/4-inch thick. Roll up the dough using a rolling pin
, and gently lift and place it over a deep, 10-inch tart pan
. Gently press the dough
into all the crevices and trim the overhang to 1/2-inch. Crimp the edges for a decorative finish and use the trimmed dough to patch any holes.
Dock the bottom of the crust with a fork to keep it from puffing up, line with parchment paper and add dried beans to act as pie weights
. Place on a large baking sheet and bake until the crust begins to brown, 20 to 30 minutes. Remove the parchment and dried beans
For the custard
the butter in a large saute pan over medium heat and saute the leeks
until they soften and begin to caramelize
, stirring occasionally, 8 to 10 minutes. Remove from the heat, cool and reserve.
the cream, milk
, cornstarch, salt, pepper, cayenne, nutmeg
and eggs in a large mixing bowl. Scatter the leeks evenly over the bottom of the crust
. Top with the cheese and ham. Pour the custard over the top and place in the oven on a large sheet tray.
Bake until the center is set and the crust is golden brown, 40 to 45 minutes. Let cool on a wire rack. Serve warm or at room temperature.