3 medium sweet potatoes
1 teaspoon olive oil
2 shallots, finely chopped
1/2 cup fat-free ricotta cheese
1/4 teaspoon salt
1/4 teaspoon ground black pepper
1/4 teaspoon ground ginger
1 tablespoon brown sugar
1/4 cup grated Parmesan cheese
2 1/2 tablespoons chopped fresh sage