Whisk the cream with the egg yolk and place in a pan. Bring to a boil and melt a teaspoon of grated hard cheese in it. The whole thing should be a bit creamy.
Cook the pasta according to the instructions on the packet.
Let the truffle butter melt in the open glass in a water bath, add to the cream and stir well. Carefully season with a little pepper and salt and add some cheese if necessary. Don`t let it boil anymore. Add the truffle oil and stir well.
Drain the pasta and add portion by portion to the pan with the truffle cream, turn in it and distribute on plates.
If you like (and depending on your budget), you can rub a fresh truffle over it. But it is not absolutely necessary - it tastes very truffle even without it.
Depending on their taste, everyone at the table spices up their own taste with the cheese from the mill, pepper and salt, as the tastes are known to be very different.