Preheat the Instant Pot on High Saute.
Combine the potatoes and butternut squash in an ovenproof bowl that will fit into the Instant Pot liner. (You can do all squash, all potatoes, all sweet potatoes, all turnips, or a mix of any of the above!) Cover with foil.
Cut the pork tenderloin pieces into four even pieces (8 pieces total.)
Season the meat with about half of the Yankee Pot Roast seasoning, or, liberally with pepper, rosemary, garlic, and thyme.
Add oil to the hot pot.
Sear each piece of pork, about 3 minutes per side. You might have to do this in batches. Remove from the pot.
Add about a tablespoon more butter, and saute the mushrooms, minced onion or onion flakes (if using your own blend), and garlic until browned and fragrant.
Add hot beef broth, soy sauce, and the rest of the seasoning blend. Scrape the pot to get all the flavor into the broth (The hot cooking liquid helps the pot come to pressure much faster.)
Return the meat to the pot.
Stack a trivet/rack into the Instant Pot, on top of the meat.
Stack the bowl of squash/potatoes on top of the trivet/rack.
Lock the lid, turn the knob to Sealing.
Press the Manual or Pressure Cook button and adjust the time to 20 minutes.
When pressure cooking has completed, carefully release the pressure (a quick release), or allow a natural pressure release (whatever you have time for.)
Remove the bowl of potatoes with an oven mitt. If there’s a lot of liquid in the bowl, strain it out.
Mash the potatoes in the bowl with butter, heavy cream or milk, and salt to taste.
Remove the meat onto a serving platter to rest for a couple minutes. Slice into 1/2 inch pieces, if desired.
Set the Instant Pot to High Saute.
Taste the broth and add more soy sauce, beef or chicken bouillon, pepper, garlic, or seasoning to taste.
Combine the cornstarch and heavy cream to make a paste.
When the liquid comes to a boil, whisk the heavy cream mixture into the gravy to thicken.
Turn off the Instant Pot/remove from heat immediately and serve. Enjoy with Instant Pot Cranberry Sauce or Instant Pot Steamed Broccoli!