Heat a large 12″ skillet or fry pan over medium-high heat and add the olive oil. Allow the oil to heat up for 1-2 minutes before adding the diced onion and minced garlic.Sauté the onion and garlic for a couple of minutes before adding the sausage rounds. Fry the sausage until brown and crispy, about 5 minutes.
Add the pasta, cauliflower, stock, milk and flour. Stir everything together until combined, being sure the flour is thoroughly dispersed into the liquid. Bring the mixture to a boil, then turn down to simmer over low-medium heat for 10-11 minutes, or until the pasta is fork-tender.*** Keep the lid on, with a slight crack to allow steam to escape.
Turn the heat to low, and add the frozen peas and parmesan cheese. Stir to combine and cook for 5 minutes. Serve immediately, topping with crispy onions and black pepper for garnish.
Leftovers can be stored in an airtight container, for up to 2 days, or frozen for up to 2 months. Store the leftovers without the crispy onions.