Preheat the oven to 350 F. In a shallow dish combine the sesame seeds, flour, salt and cayenne to taste. Dredge the chicken in the mixture, gently patting the coating onto it. In a large skillet, heat the butter and oil over moderate heat until hot. Add the chicken and cook it for 4 minutes on each side, or until golden brown. Transfer chicken to a platter. Add the flour to the skillet and cook it for 2 minutes. Add the chicken stock and cream and bring the mixture to a boil, stirring. Simmer the mixture until lightly thickened and season with the mustard and salt and pepper to taste. Arrange the chicken in a buttered baking dish, spoon the sauce over it and sprinkle with the bread crumbs. Bake, covered, with foil, for 30 minutes. Uncover and bake for 10 to 15 minutes more.