Set Instant Pot to sauté preset. To the pot add olive oil, carrots, celery, onion and bacon. Sauté for 5 to 6 minutes or until the vegetables have softened and beginning to brown.
Next, add ground beef, sausage, salt, onion powder, Italian seasoning, pepper, and red pepper flakes. Mix well. Continue to cook on sauté preset, until no pink remains.
To the beef add diced tomatoes, tomato puree, chicken stock and tomato paste. Mix well, until tomato paste has melted. Add bay leaves.
Set Instant Pot to High-Pressure cooking for 20 minutes. (Make sure the valve is closed)
After 20 minutes, quick release the pressure. Remove bay leaves, then add the cream. Mix until fully blended. Thicken further with additional tomato paste, adding 1 Tbsp at a time. Repeat until desired consistency is reached.
Serve immediately ladled over cooked spaghetti, rigatoni, pappardelle, or tagliatelle. Top with grated Parmesan cheese, if desired.