Mama has lots of breakfast potato recipes. You can use your leftover mashed potatoes to make potato cakes or make some homemade hashbrowns.
Hashbrowns

4-5 medium potatoes
1 small onion, finely chopped
1 teaspoon garlic powder
1 teaspoon salt
1/2 teaspoon pepper
3 tablespoons olive oil
3 tablespoons butter
Julienne potatoes ( cut into small long strips by first cutting the potato in slices and then cut the slices into strips) and place in cold water until ready to use to keep them from turning brown.
Sautee' onion in 1 tablesppon olive oil and 1 tablespoon butter in a large pan until soft and tender. Remove onion from pan and set aside.
Drain the potatoes
Add remaining live oil and butter to pan. Turn the heat to medium high and add the potatoes, salt, pepper and garlic powder.
Allow the potatoes to cook until they turn glden brown on the bottom. Using a spatula, turn sections of the potatoes over until all of the browned potatoes are on top. Again, allow the potatoes to brown. Push the browned potatoes off to the side and flip the potatoes once again (making sure that the uncooked poatoes are on the bottom of the pan).
Add onions and cook until brown and potatoes are tender.
Potato Cakes

This is great for using up those leftover mashed potatoes. You might even want to make some extra taters for friday nights supper just so you can make these on the weekend.
2 cups mashed potatoes (I've never tried instant potatoes so I have no idea if those will work)
2 eggs, slightly beaten
2 tablespoons dried chives
1/4 cup flour
Mix all ingredients together in a bowl. Using a large spoon, drop by spoonful on a well greased non-stick pan. Cook over medium heat until golden brown, flip and cook other side until golden brown.
**For added flavor, you can add some bacon bits and shredded cheese to the batter before cooking.