Christmas Eve Kuchen

The distinctive aroma of this pie tells us its Christmas Eve in our home. It's the only time I make this during the year, which speaks to the traditionalist in me. I should give in once in a while. This pie should be enjoyed more than once a year. You can decide that for yourself.

Ingredients

cups Flour, All Purpose, UnbleachedScant
1 tsp White Sugar
1 tsp Salt
1 tbsp YeastOr, one envelope of dry yeast
½ cup MilkLukewarm
2 tbsp Unsalted ButterSoftened
4 cups LeeksAbout 3 medium size, well washed and sliced about one quarter inch slices
3   Potatoes, WhiteWashed and fairly thinly sliced
2 tbsp Classic Olive Oil
½ cup Yellow OnionSliced thinly
1 tbsp Mustard, preparedApproximately; we like some of the seedier ones such as Grey Poupon Country Style
½ lb. FontinaApproximately, sliced thinly
2   Egg/s
½ cup Half and Half Cream
½ cup Sour Cream

Directions

1 This pie takes about three hours to prepare, start to finish. It needs to bake a good forty minutes.
2 First, the crust:
3 In a small bowl, put the flour, 1/2 teaspoon of the salt, sugar, and yeast. Blend together. Add the warmed milk and softened butter. The milk should be just warm to the touch so as not to interfere with the yeast. Mix these together until the batter is smooth. Add the remaining flour, stirring it well. You may then knead it a bit on a very lightly floured surface. However, I have also left out the kneading with good success. Replace the dough in the bowl; cover with plastic wrap and let it rise for about an hour or until it's just about doubled in bulk. You don't have to be too particular about that.
4 In the meantime, for the filling:
5 Boil the potatoes briefly, perhaps for ten minutes, so they are somewhat al dente. Again, don't worry about this if the potatoes get a little more cooked. It's just that you are going to layer them in the pie and it's helpful to have them keep their shape somewhat. Drain the potatoes, if needed. (I cook my potatoes in just enough water so that it evaporates by the time the potatoes are cooked. I think that way the potatoes retain the best flavor.)
6 The leeks: I used to suffer so over washing them. I have found recently that if I just cut off the hairy end and take off the outer leaves, slice a few inches, take off a few more outer leaves, wash off any dirt, slice some more, and so on, the result is sliced ungritty leeks without too much hassle. I use a good portion of each leek, right up to the soft yellowish green part. In a medium size fry pan over medium heat, pour in the olive oil. Let it heat some and then add the leeks and sliced onions, sauteing them until they become somewhat limp, but not browned on the bottom. They'll need a little stirring.
7 Composing the dish:
8 I use a ten inch Corning Ware tart dish. Preheat the oven to 350 degrees.
9 For the dough, deflate it some and place on lightly floured surface. With a rolling pin, roll it out so that it is a few inches larger than the baking dish. Gently, perhaps rolling the dough over the rolling pin, lift the dough into the tart dish, keeping the edge somewhat over the rim. I don't get too fancy with fluting.
10 Spread the mustard over the bottom, somewhat to your preference. It does blend will with the flavors.
11 Make layers starting with half the sauteed leeks, half the potato, half the fontina and parmesan. Repeat the layers.
12 For the sauce, mix together the eggs, the rest of the salt, cayenne pepper (if using), half and half, and the sour cream. Pour this over the other ingredients.
13 Place in oven. Lower the temperature to about 335 degrees, and bake approximately forty to fifty minutes, or until the filling is a bit puffed and a rich golden brown.
14 I hope it's wonderful.
15 We serve this with a mesclun salad. A taste of fruit is nice too, perhaps some sliced pear.