1/2 c. butter
1 c. brown sugar, packed
1/4 c. Pet milk
1 3/4 to 2 c. confectioners' sugar (I don't use quite that much)
1 tsp. butternut flavoring

Melt butter in saucepan. Stir in brown sugar. Boil and stir over low heat 2 minutes. Stir in milk. Bring to boil, stirring constantly. Cool to lukewarm (120 degrees). Gradually stir in confectioners' sugar. Place pan in ice water and stir until thick enough to spread. Add 1 teaspoon butternut flavoring. Enough for two 8 or 9-inch layers or 9x13 inch oblong.