Heat up the oil in a pan, add the butter and allow it to melt.
Chop the onion and garlic, and add them to the pan.
Cook for 2-3 minutes until the onion has soften, then add the sliced mushrooms, and leave to cook for 4-5 minutes until nicely browned, and all the liquid released.
Add the pancetta, give it a good stir, and leave to cook until crispy.
The ground chicken can now be added too, just give it a good stir until the meat is no longer pink.
Add the chopped tomatoes, tomato puree, chicken broth, seasoning, and leave to cook with the lid on until the sauce is reduced.
Meanwhile, cook the tagliatelle according to the packet instructions.
When ready, drain the water, then add it to the pan with the sauce.
Garnish with freshly-chopped parsley.