Mashed Potato Fudge

3 sq. unsweetened chocolate
1 stick butter
1/2 c. mashed potatoes (instant work well)
1 tsp. vanilla
1 lb. powdered sugar
1 c. nuts, chopped (optional)

Melt chocolate and butter in heavy saucepan.
Combine sugar, salt and vanilla in a bowl; add mashed potatoes and nuts.
Add melted chocolate mixture.
Mix well.
Put in greased or buttered 6 x 10 inch pan.
Let set until firm and cut into squares. Very good!