Preheat oven to 375F.
Put the chicken breasts in a baking sheet and rub them with oil. Sprinkle with salt and pepper. Bake for 35 to 40 minutes until thoroughly cooked. Let them cool and then dice into ¾ inch cubes.
Heat the chicken stock and dissolve chicken bouillon cubes. Ina large pot, melt butter and sauté onion for 10 minutes. Add flour, stir continuously and cook for 2 minutes.
Add the chicken stock and simmer over low heat until thick. Add salt, pepper, and cream. Add chicken, carrot, onion, peas, and parsley. Mix well.
Pour the mixture to a 10x13x2 inch baking dish. Arrange thedish on a sheet pan lined with aluminum foil.
Add a sheet of puff pastry on the baking dish of chicken and vegetables mixture. Cut slits on the pastry for steam to escape. Brush with egg wash. Bake for 30 to 40 minutes. Serve hot!