Chocolate Potato Cake

I had this for breakfast today. :)

4 oz unsweetened chocolate
1 tsp. vanilla extract
2 cups cake flour (I just used regular flour)
1 tsp. baking flour
1/2 tsp. baking soda
1/2 tsp. salt
1/2 tsp. cinnamon
1 cup butter
1 3/4 cups sugar
4 eggs
1 cup mashed potatoes (probably shouldn't use instant: different consistency)
1 cup buttermilk (put 1T white vinegar or lemon juice in a 1c. measure, then fill the rest with milk)

Melt chocolate with the vanilla, cool slightly. Sift together the flour, baking powder, soda, salt, and cinnamon. Cream the butter and sugar and beat in the eggs one by one. Add the chocolate and mashed potatoes. Beat in the dry ingredients alternatively with the buttermilk. Pour into a greased 13x9inch pan and bake in a preheated 350 degree oven for approximately 40 minutes (or bake in 2 round 9 inch pans for 30-35 minutes.) Cool before frosting.