In a Dutch oven cook lamb, half at a time, in margarine and olive oil till brown. Add the onions, mushrooms, 1 cup of the apple cider, coriander, mustard, and pepper. Simmer, covered for 15 minutes. Add carrots and apples. Cook for 20 minutes more.
Stir together the flour and remaining apple cier. Add to the hot mixture. cook and stir till thickened and bubbly. Transfer to a 12x7x2-inch backing dish.
Roll pastry to a 12x10-inch rectangle. Cut two 12x3/4 inch strips. Place each strip on long edges of baking dish. Combine egg and light cream. Brush tops of strips with egg mixture; cut remaining pastry to fit top of dish. Place atop pastry strips; crimp edges. Brush pastry with egg mixture.
Bake in a 400 F oven for 15 minutes.