Set the Instant Pot to saute.
When hot, add oil, mushrooms, onions, and garlic. Saute until onions are translucent.
Select cancel on your Instant Pot to stop the saute function.
Add the broth, Dijon mustard, paprika and Worcestershire. Ensure there are no onion or mushroom bits stuck to the bottom of the liner.
Place the trivet that came with your Instant Pot into the broth. Place the pork loin on the trivet.
Place a collapsible petal steamer on top of the pork.
Add the quartered potatoes to the steamer rack.
Secure the lid and seal the pot.
Set the Instant Pot to high pressure for 20 minutes.
Quick release the pressure when pressure cycle is done.
Lift the steamer rack with the potatoes out of the pot, and place into a large bowl.
Using a meat thermometer, check that the pork temperature is at least 145°F. Remove from the liner and cover with foil and let sit for 5-10 minutes.
Meanwhile, add the cream and butter to the potatoes and mash to desired consistency. Add cream until desired texture is achieved.
Set the Instant Pot to saute and stir in the flour slurry ( 2 tbsp flour and water combined in a small bowl) and heat until thickened. If you want a thicker gravy, mix up a second slurry and add that in.
Slice pork and pour gravy over top.