Preheat oven at 350 degrees.
Cube potatoes (Remove skin, if desired).
Place cubed potatoes, water, salt, pepper and 1 stick of butter in Instant Pot.
Press "pressure cook" and add 6 minutes to the timer. Make sure the Instant Pot is on "high pressure", and that the release valve is turned towards "sealing". It will take a few minutes for the Instant Pot to warm up.
Wait until the timer has completed the 6 minute countdown, then do the quick release to relieve pressure. BE VERY CAREFUL! The air released will be VERY hot!
Once pressure is released, remove lid. Add butter and milk.
Mix potatoes and other ingredients with an electric hand mixer or a potato masher.
Add sour cream and ranch mix. Mix well.
Fold in half shredded cheese, half green onion and half bacon crumbles.
Place mixture in baking dish.
Top with remaining cheese, bacon and green onion.
Bake at 350 degrees for 20 minutes or until cheese is melted, golden and bubbly!