Boil spinach and Swiss chard in salted water for 10 minutes.

Drain spinach and Swiss chard, cool, squeeze dry, and chop finely.

In a bowl, combine the chopped greens, ricotta, gorgonzola, egg yolks, and two-thirds of the Parmesan cheese.

Season the mixture with salt, pepper, and nutmeg.

Spread flour on a board.

Take a tablespoon of the ravioli mixture and roll it in the flour to form a small ball.

Drop 5-6 balls into a pot of boiling water and cook for 30 seconds, or until they float to the top.

Remove cooked ravioli.

Repeat the process until all ravioli balls are cooked.

Melt butter over low heat.

Serve the ravioli immediately, topped with melted butter, leftover Parmesan cheese, and sage leaves.