For chard dumplings, place flour on countertop and make a well in the center. Mix eggs, olive oil and salt with a fork and gradually incorporate into the flour. While doing this, turn the dough over to the other side several times with the scraper and knead together neatly with your hands. Knead the dough for 15 minutes, perhaps adding a few tablespoons of water until the dough is shiny. Then wrap in plastic wrap and let rest at room temperature for an hour.
Wash fresh chard and blanch or steam briefly. Squeeze and pat dry.
Sauté the diced onion in ten grams of butter and fry with the ricotta, chard, chopped garlic, Parmesan and mortadella to form a farce. Then season with salt, pepper and nutmeg.
Dust the work surface with flour. Roll out the dough thinly and cut into eight-centimeter squares with a wavy pastry wheel. Spread the filling, leaving the edges of the dough free. Mix the egg yolk with a tablespoon of water and brush the edges of the dough with it.
Fold the squares into triangles and simmer in enough boiling hot salted water until they float to the surface.
Melt 100 grams of butter. Pluck the sage and add to the butter.
Toss the chard dumplings in the sage butter, serve on preheated pasta plates and sprinkle with Parmesan.