Cook potatoes and carrots together in boiling salted water until just tender. Drain; set aside.
In a small skillet, melt 1 T. of the butter and saute onions over medium heat until lightly brown. Lower heat. Sprinkle onions with sugar; toss lightly. Add white wine; cook until almost all liquid is absorbed. Remove from heat; set aside.
In a large saucepan, over low heat, melt remaining 3 T. butter. Add flour to make a roux and whisk for 3 minutes. Add the stock, whisking constantly. Mixture should thicken considerably. Raise heat slightly. Add cream, stirring constantly. Lower heat. Cook and stir 1 minute longer.
Add potatoes, carrots, onions, beef, peas, cayenne, and allspice. Add salt and pepper to taste. Mix well; remove from heat.
Spoon mixture into a 2-quart casserole dish. Sprinkle with parsley and chives.
Roll out pie dough and place over top of casserole. Build up the edges high and pinch into rim of dish. Cut a slit in the top to allow steam to escape. Brush egg yolk over the crust. Bake in preheated 450 degree oven for 10 minutes; reduce heat to 375 degrees. Bake 20 minutes longer. Let stand 5 minutes before serving.