Peel and finely dice the onion. Clean the mushrooms and cut them into leaves.
Melt the butter and fry the onion cubes until golden. Now add the mushrooms and fry them well, then squeeze in a clove of garlic. Let the liquid evaporate and season everything vigorously with salt and pepper. Add the coffee cream and cover and let simmer for about 10 minutes.
In the meantime, bring the water with the second clove of garlic and salt to the boil and cook the tagliatelle in it according to the instructions on the packet al dente. Drain.
Whisk the egg yolks with white wine and mix the mushrooms with them. Then arrange immediately on the pasta and serve.
Tip: If you want, you can sprinkle fresh chives on top.