Switch on your instant pot and press sauté (normal). Wait for the display to show HOT, then add the butter to the inner steel insert.
When the butter melts, add the garlic and sauté until it is slightly browned.
Add the potatoes, broth and salt and mix well. Cancel sauté.
Secure the lid, make sure the steam release handle is sealed and press the pressure cooking button ('manual' in some models). Set it on high for 1 minute. While the potatoes are cooking, switch on your oven and pre-heat it on the broiler setting.
When the timer beeps, wait for 5 minutes and then release pressure. Remove the potatoes from the instant pot with a slotted spoon straight into a baking dish. Don't discard the remaining liquid in the pot.
In the remaining liquid in the pot, add the heavy cream, grated cheddar cheese and sour cream. Also add paprika, black pepper and oregano. Mix everything well. The cheese will melt in the residual heat from the pot.
Pour this sauce on top of the potatoes that you transferred earlier to the baking dish. Top with some more cheese and keep in the oven for 3 minutes.
At about 3 minutes, you will see the cheese forming a brown crust on top. Remove from the oven and serve warm.