Coconut Cream Cake
["1 box cake mix of your choice, cooked", "1/4 c. sugar", "1 Tbsp. cornstarch", "1/4 tsp. salt", "1 c. milk", "1 egg yolk, slightly beaten", "1 Tbsp. butter", "1 tsp. vanilla"]
["Mix sugar, cornstarch and salt in a saucepan.", "Gradually stir in milk.", "Bring to a boil over medium heat, stirring constantly. Boil 1 minute.", "Remove from heat.", "Stir at least 1/2 of mixture into egg yolk.", "Blend into remaining mixture.", "Boil 1 minute more. Remove from heat; blend in butter and vanilla.", "Add coconut to taste.", "Cool, stirring occasionally.", "Spread between layers and frost with 7 Minute Frosting."]
["cake mix of", "sugar", "cornstarch", "salt", "milk", "egg yolk", "butter", "vanilla"]