Finely chop the mushroom, onion and garlic, by knife or in a food processor. Add to the instant pot. (Alternatively, You can cook the onion and garlic in 1/4 cup broth or wine on saute, for a few mins for additional flavor and then add mushrooms).
Add the spices, herbs, 1 tsp rosemary, salt, Worcestershire (or use 1 tablespoon soy sauce and 2 tablespoons red wine) and 1 cup broth. .(Additional flavors such as poultry seasoning, herbs can be added at this point. Use bouillon with water instead of broth.)
Mix well to combine. The mixture will look dry but mushrooms leak a ton of moisture under pressure. See stove top instructions in notes.
Close the lid. Pressure cook for 20 mins. Let the pressure release naturally. Open the lid.
Start saute. Add more fresh rosemary, white pepper. Mix starch in 1.5 cups of broth and add in. Bring to a boil. Add 1/2 cup cashew cream for creamier (optional), or use a nutfree non dairy cream or 1 tbsp toasted flour(wheat or rice) mixed in 1/4 cup broth for additional thickening). Taste and adjust salt and flavor by adding more if needed. Add some soy sauce if needed. Simmer for another 1-2 mins.
Stovetop: Saute onion and garlic in 1/4 cup broth or 2 tsp oil until translucent. Add chopped mushroom and a good pinch of salt and continue to cook until brown on some edges(10 10 15 mins). Stir occasionally, Deglaze with broth if needed. Add the spices, herbs, salt, Worcestershire and 1/4 cup broth and cook for a few mins. Mix starch in 2 cups of broth and add to the pan. Simmer for 5 mins or longer until desired consistency. Taste and adjust flavor.