Spread butterscotch filling on cooled cake to within 1/2 inch of edges.
Frost sides and top of cake with marshmallow frosting. Melt 1/2 square of unsweetened chocolate. Dip back of a spoon into chocolate and swirl into frosting.
Butterscotch Filling
1 cup brown sugar (packed)
3 Tbsp four
3/4 cup light cream
2 Tbsp butter
1 tsp. vanilla
In a medium saucepan mix brown sugar and flour. Gradually stir in the cream. Heat to boiling, stirring constantly. Boil and stir for one minute.
Remove from heat, blend in the butter and vanilla. Cool.
Marshmallow Frosting
2 egg whites
1 1/2 cups sugar
1/4 tsp cream of tartar
1 Tbsp light corn syrup
1/3 cup water
3/4 cup marshmallow creme
In top of double boiler, combine egg whites, sugar, cream of tartar, corn syrup and water. Place over boiling water; beat until stiff peaks form, scraping pan occasionally. Remove from heat; add marshmallow cream. Beat until of spreading consistency.