Bechamel Sauce

Melt butter and oil over low fire. Remove from fire and stir in the flour, blending thoroughly. Return to fire and when the mixture starts bubbling, remove to side of fire and add 1/3 cup of milk very gradually, stirring constantly to prevent the mixture from becoming lumpy. Return to low fire, cook stirring and increasing the sauce in small doses with stock, remaining milk and seasoning, until the desired thickness is obtained. Beat egg and add to sauce (optional). Serves 4 - 6.