Mix cornstarch and coffee in saucepan until smooth. Add 1/2 cup sugar and cook
over low heat, stirring constantly until thickened. Add raisins and nuts and set
aside while preparing batter.
Beat butter until soft and fluffy. Add brown sugar and remaining white sugar
and continue beating until thick and light in color. Add cream of tartar and baking
soda together and add alternately with milk. Add vanilla and mix well. Pour 1/2
the batter into a buttered 8-inch square pan. Spread with raisin mixture and cover
with remaining batter.
Bake in preheated 350 degrees F oven for 40 minutes or until knife comes out clean.
Cool and turn out of pan and cut into nine squares.
Source: Cafe Cartago, Commerce City, Colorado - Specialty Recipe