Fill a pot w/ water & bring it to a boil. Add the tagliatelle & cook for about 7-8 min. Check the cooking time on the package & adjust if necessary. The pasta shall be al dente.
Start preheating the oven to 200° C w/ fan.
Grate the pecorino. You'll need 50 g altogether. So grate & divide.
Chop the pancetta roughly.
Start frying the pancetta softly in some butter w/ a pinch of salt.
Drain the pasta & put it back into the pot. Add butter & salt & mix.
Put the pasta into the pan w/ the pancetta & mix. Add the grated pecorino (1st batch) - mix again.
Finally put everything in the casserole.