Press ‘Sauté’ and add olive oil to inner pot of Instant Pot. Add onions, celery, carrots, bell peppers and garlic and saute for 3 minutes, stirring frequently.
Add fresh mushrooms and saute for 2 minutes. Turn off Instant Pot by pressing ‘Keep Warm/Cancel’.
If there’s food stuck to the bottom, deglaze pot with 2 tablespoons of water.
Add in dried porcini mushrooms, crushed tomatoes, black pepper, salt, thyme, oregano, basil, sugar, balsamic vinegar, tomato paste, crushed red pepper, pasta, milk, wine and water. Stir to combine.
Close Instant Pot Lid, and make sure steam release handle is in the ‘Sealing’ position. Cook on 'Manual' mode for 7 minutes. Do a quick release of pressure. There might seem to be more liquid than you’d like, but don’t worry, the liquid will get absorbed by the pasta.
Stir in mascarpone cheese. Let the pasta rest for a few minutes and it will thicken up.
Sprinkle each serving with Parmesan and fresh parsley.