1. In a medium saucepan over medium heat, bring milk, butter, sugar and salt to a low simmer. Remove from heat and pour into large mixing bowl of a stand mixer. Stir in cold water bring temperature to lukewarm.
2. When milk mixture is the right temperature, sprinkle over yeast. Let stand 2 minutes, then stir in completely. Let stand 5 minutes until foamy.
3. With the dough hook attachment to the stand mixer, stir mashed potatoes and beaten eggs into yeast mixture. Slowly add flour and mix until a soft dough is formed, about 5 minutes. Continue beating until dough is shiny and elastic and comes away from sides of bowl, about 10 minutes, or knead bread by hand on a lightly floured work surface.
4. Place dough back in bowl, cover with a warm, damp cloth and let rise in a warm place for 1 hour or until doubled in size.
5. Punch down dough and knead for 5 minutes. Shape dough into 3 loaves and place in 3 lightly oiled bread pans. Cover loaves and let rise for 45 minutes or until doubled.
6. Meanwhile, preheat oven to 400oF. Place loaves in oven and bake for 10 minutes; reduce heat to 350oF and bake for 30 minutes or until lightly browned and bread sounds hollow when tapped on.
7. Remove bread from pans and cool on rack. Serve warm with butter and jam.