Heat olive oil in the instant pot on the hottest saute function. Dice onions, carrots, celery. Cook for 8-10min.
Add ground beef with salt and freshly ground pepper. Sauté, breaking the meat until brown and most of the juices evaporated.
Add garlic and tomato paste, cook for 1 minute.
Stir in crushed tomatoes, water, 1/2 parsley. Bring to simmer. Place instant pot lid and set High Pressure for 20 minutes.
Quick release. Switch to lowest sauté setting and bring to bubble uncovered. Simmer 5-10 minutes until the sauce is thickened.
Stir in heavy cream, 1/2 parsley, nutmeg. Season with salt and pepper.
Serve with spaghetti and hard cheese.