Turn Instant Pot on to saute mode, wait for display to read "Hot" then add butter, onions, and garlic. Saute for 1-2 minutes, stirring frequently.
Add salt, pepper, and broth.
Add shredded potatoes to steamer basket and set basket in Instant Pot on top of the onions and broth.
Secure the lid and turn pressure valve to seal. Cook on manual high pressure for 1 minute.
When cook time ends, quick release the pressure. Pour potatoes into pot and set steamer basket aside. Add the sour cream and cheese. Stir to combine.
Transfer to a small baking dish (8 inch square or similar) and top with bread crumbs or cereal.
Broil in oven for 2-3 minutes to brown the topping.
Remove from oven and serve. Top with additional cheese, if desired.