Potato Bread: In cup, dissolve yeast and sugar in warm water. In bowl, cut flour, salt and butter together. Stir in the milk, egg and mashed potatoes into yeast mixture. Add mixture to flour gradually to make stiff dough. Knead until smooth. Place in greased bowl and let rise.
Spinach Bread: Cook and puree spinach. Prepare the bread same as potato and tomato bread substituting spinach.
Tomato Bread: Prepare the bread following the directions for the potato bread, dissolving the yeast in 1 tbsp. of water and substituting the mashed potatoes for the tomato sauce.
To make marbled loaves: When all three breads have doubled in bulk, punch them down and let rest, covered for 5 minutes. Lightly grease 3 baking pans. Divide each into 3 equal pieces. On lightly floured surface, roll, shape, and stack your dough any way you like. Have fun! Cover each loaf with an oiled plastic wrap and set aside in warm place until doubled, about 45 minutes. Preheat oven to 375 degrees. Bake the loaves 35-40 minutes. Transfer to wire rack. Makes 3 loaves (12 pieces each).