Marshmallow Brownie Cookies

1/2 cup butter or margarine
1 cup granulated sugar
1 egg
1 teaspoon vanilla
1 3/4 cups flour
1/2 teaspoon salt
1/2 teaspoon baking soda
1/2 cup cocoa
1/2 cup milk
1/2 cup chopped nuts (opt.)
Large marshmallows, cut into thirds

Cream together butter and sugar. Add egg and vanilla and mix well. Sift together flour, salt, soda, and cocoa. Add dry ingredients to mixture alternating with the milk. Stir in nuts. Drop by teaspoonfuls onto a greased cookie sheet approximately 2 inches apart. Bake at 350 degrees for 9 minutes and remove from oven. Immediately place a marshmallow piece on the top of each cookie and bake for 2 more minutes. When cookies are cool, frost each cookie with chocolate icing.
Chocolate Icing:
1/2 cup margarine
3 tablespoons milk
1 teaspoon vanilla
1/3 cup cocoa
4 cups powdered sugar

Mix ingredients together well and frost tops of cooled cookies.