Recipe(tried): April - Penuche Nut Frosting (Brown Sugar Frosting)

April, I think this is what you are looking for and you are right...after it has cooled and set up it does crack when you touch it.
We had this all the time on spice cake when I was growing up. Mom usually left out the nuts but it would be good.

Penuche Nut Frosting (Brown Sugar Frosting)

1 cup brown sugar, firmly packed
1/4 cup milk
1/4 cup vegetable shortening (Crisco)
1/4 tsp. salt
1/2 tsp. vanilla extract
1/2 cup chopped nuts

Place brown sugar, milk, vegetable shortening and salt in a saucepan. Bring slowly to a full rolling boil,stirring constantly, and boil 1 minute. Remove from heat; beat until lukewarm. Add vanilla; beat until thick enough to spread. The mixture may still be warm. If frosting becomes too thick, add a little cream. Add nuts; spread on cake. Frosts the top of an 8"x8"x2" cake.
This recipe is from the Good Housekeeping Cook Book from 1942 (it was Mom's and it has some of the best old recipes in it.)