Boil the tagliatelle in salted water.
For the sauce, chop the meat finely and put it to braise in oil in a pan.
Chop the mushrooms and add them as well, season with salt and pepper.
When they're almost done, add the chopped garlic and finally the cream that you've mixed with the mustard.
Leave for another few min. on the stove and it's ready.
Distribute the tagliatelle in plates and pour on the sauce.