In the bottom of your pressure cooker, place cauliflower, onion, garlic, celery and water. Top with pork roast and season with sea salt & pepper.
Cook under pressure for 90 minutes if your roast is frozen, 60 minutes if completely thawed. Quick depressurize following manufactures directions.
Carefully remove pork roast from the pressure cooker and place in an oven proof dish. Bake at 400 degrees while preparing the gravy, this helps to render the fat and crisp up the edges of the pork to be more like as if it was slow roasted.
Transfer cooked vegetables and broth to your blender and blend until smooth, set aside.
In your (dirty) pressure cooker (on the saute function) cook mushrooms in coconut oil until soft, roughly 3-5 minutes. Add blended vegetables and continue to cook on the saute function until it is thickened as desired.
Serve mushroom gravy over shredded pork.