In a large bowl dissolve the yeast in 3/4 cup of the water.
Add in 3 tablespoons flour. Cover and let rise for 30 mins.
Stir in remaining 3/4 cup water, salt, caraway seed. Gradually add mashed potato and flour. Knead about 10 minutes.
Place in a well greased bowl and let rise until doubled in size (1 1/2 hours)
Punch down. Knead about 4 minutes. Place in a loaf pan. Flatten to fit and let rise again until double in size (30 mins)
Brush top with water and cut 1/4 inch deep cross and bake 1 to 1 1/4 hours at 375 F