dee dee's chicken pot pie

Ingredients

• 1 pound chicken breasts, boneless and skinless (you can use dark meat if desired) cut into bite size pieces
• 1/4 cup butter
• - salt and pepper
• 3 tablespoons olive oil, extra virgin (can use butter or vegetable oil)
• 1/2 large onion, chopped
• 1 stalk celery, sliced
• 2 medium potatoes, peeled and cubed
• 3 - carrots, sliced
• 1/2 cup corn kernels, fresh (can use frozen)
• 1/2 cup green peas, frozen
• 1/2 teaspoon thyme, dried
• 1/4 cup all purpose flour
• 1 1/2 to 2 cups milk
• 1/2 cup heavy cream
• 2 - chicken bouillon cubes, crushed (or 2 to 3 tsp granulated)
• 4 ounces pasteurized cheese (like velveeta) optional
• 1 sheet pastry dough, rolled out to 9 x 9 square