Cook baby spinach in a small amount of water. Drain and bring to room temperature. Squeeze as much water out as possible.
Drain ricotta in a strained lined with cheesecloth over a small bowl to catch liquid for ~1 hour. Facilitate draining by placing a heavy can on top of cheesecloth encased ricotta.
Chop drained spinach finely and combine in a medium bowl with drained ricotta. Add 2 egg yolks, salt and pepper and nutmeg and stir to combine. Add 1/4-1/2 cup flour, a little at a time, to make a sticky dough. Cover with plastic wrap and refrigerate for about 1 hour. Bring a large pot of water to a rolling boil. Shape dough into small logs, about 1-2" long using rounded tablespoonfuls of dough. Place on floured waxed paper to avoid sticking. Drop gnocchi logs into boiling water, do this in
batches so as not to overcrowd water. Once gnocchi float to the surface cook for 2 more minutes and then remove with a slotted spoon. Place cooked gnocchi in a caserole dish into which you have melted 3 Tbs of butter and stirred in dried sage. Arrange gnocchi in a single layer, cover with additional parmesan cheese and bake in a preheated 350 F oven for 20-30 minutes, until cheese is golden. Serve hot.