Ingredients
1-1/2 cups water
1 medium size boiling potato, peeled and diced
1/2 cup milk, scalded
2 cups granulated sugar
1 pkg. active dry yeast
1/4 cup very warm water
5 cups sifted all-purpose flour
1 egg, slightly beaten
6 tbsp. shortening, melted then cooled
1-1/2 tsp. salt
6 tbsp. butter or margarine
1/2 cup light brown sugar, firmly packed
1 tsp. ground cinnamon

Directions
Bring water to a boil in a small saucepan. Add the potato and cook uncovered until tender. Drain, reserving 1/2 cup of the cooking water. Mash the potato.

Combine the cooking water, mashed potato, milk and 1 cup of the granulated sugar in a large bowl. Stir until the sugar is dissolved. Cool until lukewarm.

Sprinkle the yeast into the very warm water in a 1-cup liquid measure. Stir in 1 teaspoon of the sugar. Stir until the yeast is dissolved. Allow to stand undisturbed until bubbly and double in volume, about 10 minutes.

Add the yeast mixture and 1 cup of the flour to the cooled potato mixture, then beat until smooth. Let stand in a very warm place for about 45 minutes, or until the mixture bubbles.

Beat in the egg, shortening, salt and the remaining granulated sugar. Beat in the remaining flour gradually to make a soft dough. Cover and let rise in a warm place away from drafts for about 90 minutes or until doubled in volume.

Beat the dough down and divide in half. Let rest for 10 minutes. Press into 2 greased 13x9x2-inch baking pans. Cover and let rise in a warm place away from drafts for 60 to 90 minutes or until double in volume (about 1 inch thick).

Combine the brown sugar with the cinnamon in a small bowl. Poke holes into the dough about 2 inches apart with finger. Place a knob of the butter and 1/2 teaspoon of the brown sugar mixture into each hole. Sprinkle any remaining sugar mixture over the top of the cakes.

Bake at 375 degrees F. for 20 minutes, or until golden brown. Serve warm.