Add trivet/steamer basket, cauliflower, and chicken stock to your Instant Pot. Close the lid and set the valve to sealing. Use the manual setting to cook on high pressure for 3 minutes. Use the quick release function to release the pressure. Transfer the cauliflower to a food processor. Add the butter, salt, garlic powder, and cheese and process until silky smooth. Serve immediately** with additional melted butter and freshly cracker pepper, if desired.