Chop onions into pieces about 1/2 inch or slightly larger.
Heat one tablespoon olive oil in the Instant Pot on SAUTE, MEDIUM HEAT.
Add onions and cook until they're starting to soften and brown. Then add dried basil, Greek oregano, ground fennel, Spike Seasoning and black pepper and cook a few minutes longer.
Add a little more olive oil to the Instant Pot and cook the Italian Sausage until it's well-browned and most of the liquid has evaporated. Break the sausage apart as it cooks. (Don't rush this step. The browning adds flavor.)
While sausage cooks chop mushrooms and red and green bell peppers. We made the peppers just slightly over 1/2 inch square and chopped the mushrooms into thick half-slices.
When sausage is nicely browned add mushrooms, red bell pepper, green bell pepper, canned tomatoes, Rao's Pasta Sauce, and chicken broth to the Instant Pot.
Set Instant Pot to MANUAL, HIGH HEAT, 5 minutes.
After the cooking time ends, let the stew natural release for 5 minutes.
That's it! Serve hot with some freshly-grated Parmesan to sprinkle on at the table if desired.
