Turn on Instant Pot with the Sauté button. Cook bacon in Instant Pot until crispy. Remove bacon to paper towels to absorb excess grease

Add onion and ground beef to Instant Pot. Sauté until beef is no longer pink. If there is excess grease in the pan, drain the beef and return back to the Instant Pot. Turn off the Sauté function.

Add salt, pepper, Worcestershire sauce and dry pasta. Stir until combined. Add chicken stock. Make sure all of the pasta is covered by the chicken stock by pressing down if you need to. Close and lock the lid.

Make sure the Steam Release handle on top of the lid is set to Sealing. This is required in order for the Instant Pot to build up pressure. Set the Pressure Cook button on high pressure for 5 minutes (or half the cooking time of whatever type of pasta you are using.)

When the timer is up, move the Steam Release handle to the Venting position to release the pressure. Be careful when turning this, as hot steam will shoot out. I like to use a dish towel to turn the handle. You can also leave the Instant Pot on, as it will switch over to the Keep Warm setting.

There is a small hole next to the Steam Release handle, and this is the float valve. When the silver piece is at the top of the opening, there is still pressure in the pot and you don't want to try to open it. Technically, it shouldn't unlock when the float valve is up. When the silver piece drops down in the hole, then the pressure has been released, and you can open the Instant Pot.

Add the shredded cheddar and cream cheese. Mix thoroughly. Taste to see if any additional salt and pepper are needed. Top with reserved bacon.

Let pasta sit for 5-10 minutes for sauce to thicken.