-
1
For crust, combine flour and butter in the bowl of an electric mixer.
-
2
Mix on low speed until crumbly.
-
3
Place egg yolk in a measuring cup and add enough milk to make 1/4 cup, then whisk together.
-
4
With motor running,add liquid mixture and mix just until dough holds together.
-
5
Scrape onto a sheet of waxed paper and form into a ball; flatten slightly.
-
6
Cover with a second sheet of waxed paper and roll out into a round large enough to fit into a 9 inch tart pan.
-
7
Remove top sheet of paper and lay crust loosely into pan.
-
8
Remove second sheet and fit crust into pan, trimming edges evenly.
-
9
Transfer to freezer for 15 minutes.
-
10
Heat oven to 425 degrees.
-
11
Line frozen crust with foil and weight with dried beans or pie weights.
-
12
Bake for 15 minutes in lower third of oven, remove from oven and cool on a rack.
-
13
Lower oven temperature to 400 degrees.
-
14
For filling, melt butter with oil in a large, nonstick skillet over medium heat.
-
15
Add onions and stir to coat with butter and oil.
-
16
Sprinkle with salt and mix well.
-
17
Cook, stirring often, until onions are softened, about 10 minutes.
-
18
Add Reisling and continue cooking, until onions are limp and only about 1/4 cup liquid remains.
-
19
Remove from heat and cool slightly.
-
20
Transfer onions to a mixing bowl.
-
21
Add eggs, creme fraiche, nutmeg,cayenne,and 1/2 cup Gruyere and mix well.
-
22
Scrape evenly into tart shell and sprinkle with the remaining Gruyere evenly.
-
23
Bake for 30 to 40 minutes, until top is lightly browned and a knife inserted near center comes out clean.
-
24
Cool slightly before cutting into wedges to serve.
