Preheat oven to 350° F.

Season chicken with seasoned salt and pepper. Heat oil in a large skillet over medium-high heat. Add chicken and saute until cooked through. Remove from heat and cut into chunks. Alternatively, you may use precooked chicken. Once cooked, remove chicken from pan and set aside.

Meanwhile, Cut each sheet of frozen puff pastry into 1-inch strips. On a large cookie sheet, weave strips into a lattice large enough to cover the 8-inch x 8-inch pie dish. Brush the beaten egg onto the lattice square. Bake for 10 minutes, or until dough has risen and turned light golden brown. Remove from the oven and set aside until ready to assemble the casserole.

Into the same large skillet, melt butter and then slowly add flour, stirring until consistency of peanut butter, but do not brown like a roux -- you want it to remain a golden color. Slowly add cream and keep stirring. Add chicken base, garlic, and onion and stir until thickened. Add peas, carrots, nutmeg (optional), and cut up chicken. Remove from heat. Pour the hot mixture into an 8-inch x 8-inch oven-proof pan or pie dish and top with the pre-cooked lattice square. Bake for 5 minutes or until bubbly. Any remaining pie filling may be frozen.