Step 1: Roast the sweet potatoes at 400°F for 45-60 minutes until soft. Cool, peel, and mash or rice them into a smooth puree.
Step 2: In a large bowl, combine the riced sweet potato, ricotta, salt, and nutmeg. Mix until well incorporated.
Step 3: Gradually add flour to the potato mixture, kneading gently until a soft dough forms. Avoid over-mixing.
Step 4: Roll dough into long ropes and cut into 1-inch gnocchi pieces. Optionally roll over a fork for ridges.
Step 5: Boil gnocchi in salted water until they float (about 2-3 minutes). Drain carefully.
Step 6: Melt butter in a large skillet over medium heat until it begins to brown and smells nutty. Add sage leaves and fry until crisp.
Step 7: Toss the boiled gnocchi into the brown butter sauce. Sear for 1-2 minutes until golden, then top with Parmesan and pepper.