Preheat the oven to 375 degrees F.

Pierce the sweet potatoes with a fork and bake on a sheet pan until tender, about 1 hour.

When the potatoes are cool enough to handle, halve them, scoop out the flesh and feed them through a potato ricer or food mill into a large bowl.

Stir in the ricotta, egg yolk, Parmesan, salt, pepper and 1 cup flour. Stir in additional flour in small amounts until you have a workable soft dough that is a little sticky. You may not need all the flour.

On a lightly floured work surface, take a handful of dough and roll it into a 1/2-inch thick rope. Cut the rope into 1-inch pieces and roll down the tines of the back of a fork.

Transfer the gnocchi to a sheet pan dusted with flour. Arrange them in single layer to keep them from sitting on top of each other before you cook them.

Bring a large pot of salted water to a boil.

While the water is heating, you can make the brown butter. In a large skillet, melt the butter over medium heat. The butter will turn foamy. Then look for brown specs to appear as the foam subsides. Swirl the butter a bit and it will continue to brown and smell nutty.

Quickly fry the sage leaves in the brown butter until crisp, about 20 seconds. Use tongs to remove them from the butter and take the skillet off the heat.

Cook the gnocchi in batches in the pot of boiling water for 2-3 minutes. They will float to the top when they are ready. Use a slotted spoon or spider to transfer to a bowl and cook the remaining gnocchi.

Return the brown butter to low heat and gently toss the gnocchi in the butter until they are browned at the edges.

Serve topped with fried sage and Parmesan cheese.