Clean the mushrooms and chop them if necessary. Peel and chop the onion. Cut the bacon into thin strips and drain them in a pan without fat. Add onion and mushrooms and fry in the frying fat.
Add peas, pour on cream. Cook everything for about 10 minutes. Cook pasta in boiling salted water for 8-10 minutes. Bring the sauce to the boil again, stir in the sauce thickener. Pluck the rosemary needles from the stalks, chop roughly and add to the sauce.
Season to taste with salt and pepper. Drain the pasta and rinse briefly. Arrange noodles with the sauce on a plate.