Begin by melting the butter in your Instant Pot using the Sauté function. Add the diced onion and cook until it softens, about 3-5 minutes. Stir in the minced garlic for about a minute, then press Cancel to turn off the Sauté mode.
Gently add the uncooked elbow macaroni, water, and diced ham to the pot.
Secure the lid and ensure the vent is set to the 'sealing' position. Set your Instant Pot to High Pressure for 4 minutes.
Once cooking is complete, allow a 5-minute natural pressure release, then carefully quick release any remaining pressure.
Stir in the sour cream, shredded Swiss cheese, and 2 cups of the shredded cheddar cheese until everything is wonderfully melted and creamy. Don't worry if it seems a little thin at first; the sauce will thicken as it cools.
Sprinkle the remaining 1 cup of cheddar cheese over the top, place the lid back on for a few minutes to let it melt perfectly. Remove the lid and let it stand briefly to reach its ideal thickness before serving this wholesome meal.
Notes
Nutrition per serving: Calories: 456, Total Carbs: 22g, Net Carbs: 21g, Fats: 28g, Protein: 28g.