Peanut Butter Cake

A friend made this cake for my daughter's family.  It's SO good!

Prepare 1 butter yellow cake mix in a 9x13 pan.  Cool completely.  

If the cake is not completely cool, the icing will not stay on top of the cake.

Icing:

2 cups sugar

1 stick butter

1 5oz. can evaporated milk

2 Tb. creamy peanut butter

½ tsp. vanilla

Cook sugar, butter, and evaporated milk on medium heat stirring constantly.  Bring to a boil and cook for 2 minutes.  Add peanut butter and vanilla.  Stir until melted.  Pour mixture into a bowl and, with a mixer, beat on medium-high speed for 5 minutes until glossy.  Pour the icing over the cake and allow time to cool.