In the final hour or so, cook the homemade cream of mushroom gravy, or have a can of premade cream of mushroom soup and a packet of onion soup mix ready.
Prep mushrooms by removing stems from shiitakes, then slice the shiitakes and the mini portabellas.
Melt ½ cup butter in a pot or large skillet.
Add minced shallot (or sliced green onions) and sliced mushrooms to butter. Sauté until veggies start to sweat and brown.
Add 7-½ Tbsp. of flour and stir to coat everything.
Add 1-½ cups broth (or braising liquid from pot roast) and 1-½ cups of milk, then stir.
Add salt & pepper to taste, then a packet of Lipton’s onion soup mix. Continue cooking to thicken soup.