When the farro is cooked al dente and drained from the water, add it to the skillet with the mushrooms. Stir. Add the minced rosemary and stir to combine. Taste for seasoning. Add a few grinds of the fresh pepper and one tablespoon of sherry vinegar, turn off the heat and stir.
To make the dried mushroom powder. Add a small handful of dried mushrooms to a clean spice grinder and grind to a fine powder. Continue until you used up all your dried mushrooms. Put the mushroom powder in a container with a tight-fitting lid. Store in your pantry for 3 months. This mushroom powder recipe is from My Master Recipes by Patricia Wells.