Mound the 00 flour, rye flour, and salt on a work surface or in a large bowl. Make a well in the center and add the eggs and olive oil.

Mix with a fork, gradually pulling in flour from the edges, then knead by hand for 8 to 10 minutes until the dough is smooth and elastic. Add water a teaspoon at a time if it feels dry.

Wrap the dough in plastic and let it rest at room temperature for 30 minutes.

Wilt the spinach in a dry 24 cm / 9.5-inch skillet over medium heat for 2 to 3 minutes until fully collapsed. Cool, then squeeze it hard in a kitchen towel to remove as much water as possible, and chop fine.

Stir the chopped spinach into the drained ricotta with the egg yolk, 40 g grana padano, nutmeg, salt, and pepper until evenly combined.

Roll the dough on a lightly floured surface, or through a pasta machine, to about 2 mm thick. Cut into rounds with an 8 cm / 3-inch cutter.

Spoon about 1 tsp of filling onto the center of each round. Fold in half to form a half-moon, pressing out any air before sealing the edge firmly with your fingertip or a fork. You should get about 24 to 28 pieces.

Bring a 6-quart / 5.7 L stockpot of well-salted water to a boil. Cook the schlutzkrapfen in two batches so they have room to float freely, 3 to 4 minutes per batch, until they rise to the surface and the dough is tender at the edges.

While the pasta cooks, melt the butter in a clean 24 cm / 9.5-inch skillet over medium heat, swirling often, until it turns amber and smells nutty, about 3 to 4 minutes.

Lift the cooked schlutzkrapfen straight into the browned butter with a slotted spoon and toss gently to coat.

Plate immediately, spooning extra butter over the top. Scatter with chives and the remaining grana padano, and serve right away.