Put the pasta in 4 liters of boiling water and let it simmer over high heat in an open saucepan. Cook for about 8 to 12 minutes, depending on the type of pasta. Stir in between. Then drain the pasta, rinse with cold water and drain well on a sieve.
Sort out the spinach leaves, wash thoroughly and drain well.
Now peel the onion and clove of garlic, chop finely and sweat briefly in hot butter or margarine. Add the spinach leaves, sprinkle with a little salt and sauté the vegetables in a closed saucepan over medium heat for about 10 minutes. Season the spinach with salt and pepper.
Cook the cream in a wide, shallow saucepan while stirring until it becomes creamy and about halfway down. Carefully mix the egg yolks with the cream and mix the spinach with it. Add half of the parmesan, mix everything with the pasta in a large saucepan and heat gently. Then put the dish in a shallow bowl and sprinkle with the rest of the cheese. Serve hot.