Preheat oven to 350oF. *** Base *** Grease and flour a 9x13 pan. In a large pan, melt the margarine and chocolate. Add remaining ingredients and mix well. Spread in the pan. *** Filling *** In a small bowl combine the cream cheese with remaining ingredients except for the chips. Blend until smooth and fluffy. Spread over chocolate mixture and sprinkle with chips. Bake 25-35 minutes and test with a toothpick. Remove, sprinkle with marshmellows and bake 2 minutes more. *** Frosting *** In a small pan, melt the margarine, chocolate and milk. Beat in cream cheese and powdered sugar with an electric mixer until smooth. Immediately pour over marshmellow layer and swirl together. Cut into squares.