CORNED BEEF AND CABBAGE POT PIE

1 small head green cabbage (3/4 to 1 pound), core removed and thinly sliced
3 tablespoons unsalted butter
2 medium shallots or 2 small white boiling onions, chopped
3 tablespoons flour
1 cup milk
1 1/2 tablespoon stone-ground mustard
1/4 teaspoon ground nutmeg
1/4 teaspoon dried dillweed
1/4 teaspoon ground white pepper
1 cup shredded Gruyere or Swiss cheese (4 ounces)
8 to 10 ounces cooked corned beef, sliced and cut into 4- by 1/2-inch strips
Half a 17.3-ounce package frozen puff pastry (1 sheet), thawed
1 egg, separated, for glaze

Grease a 9-inch deep dish Pyrex or ceramic pie plate.

Cook cabbage in pot of boiling water for 5 to 8 minutes, until just tender. Drain into colander and pat dry with paper towels.

In large skillet, melt butter over medium-high heat. Add shallots and cook until softened, about 2 minutes.

Sprinkle with flour and stir to coat well. Stir in milk and bring to simmer, whisking until smooth and thick, 6 minutes.

Stir in mustard, nutmeg, dill and pepper, then add cheese. Add corned beef and cabbage. Mixture will be very thick. Pour into pie plate and chill. (Can be made up to 4 hours ahead and chilled until needed.)

TO ASSEMBLE AND BAKE:
Preheat oven to 400 degrees F with rack in center position.

Dust countertop with flour and roll out sheet of puff pastry to a rectangle a bit larger than pie plate. Trim corners to round the pastry and set in freezer 20 minutes. If you want decorations, use second sheet of pastry to cut out hearts or other decorative shapes with little biscuit cutters.

Beat egg white in bowl and brush around rim of dough round; turn it over and center on the top of chilled pie filling, pressing cut edges firmly against sides of pie pan.

Beat egg yolk in bowl and lightly brush pastry with glaze. Arrange decorations, if using, and brush with glaze. Cut a few slits for steam vents.

Bake immediately in center of oven until the crust is puffed and brown and filling is hot, 35 to 40 minutes. Serve immediately.

"Be sure the filling is chilled before covering it with puff pastry. If the pastry gets too soft, it won't puff nicely. Make this in 1 large or 4 individual casseroles."

Adapted from source: Betty Rosbottom's Cooking School Cookbook by Betty Rosbottom