Poke holes in sweet potatoes with a fork. Microwave on high for 5 minutes, rotate, then cook for another 10 minutes. They should be soft at this point. If they are still hard, cook for another 5 minutes. Allow to cool enough to handle.
Remove skin from sweet potatoes and mash flesh. Ideally, you want about 2 cups of mashed sweet potato.
In bowl, combine mashed sweet potato with ricotta and parmesan cheeses along with brown sugar, salt, and nutmeg. Add flour in small amounts until a sticky ball forms. You may use less than the recommended amount.
Once dough is formed, roll a small amount of dough on a heavily floured surface into a thick rope that's about 3/4 inch in diameter. Cut into 1 inch long pieces.
Boil heavily salted water. Working with small batches, add cut gnocchi pieces to boiling water. Once they float, remove them with a slotted spoon and continue with remaining dough. This only takes a few minutes. Set aside to cool. This process can be done ahead of time.
To serve, melt butter over medium heat while stirring occasionally until brown solids begin to form and it smells wonderfully nutty. Add sage leaves and cook for a couple minutes. Add cooked gnocchi pieces and saute until heated through, 3-4 minutes, gently tossing occasionally. Serve warm.
Notes
*Note - I used whole wheat flour however I think it would have turned out even better with all purpose flour