Thinly slice the onion and finely chop the rosemary. Thickly slice the mushrooms. Heat the olive oil in a skillet over a medium heat. Add the mushrooms, rosemary and onion. Season the mushrooms with salt and pepper.
Step 2
Sautée the mushrooms for 6-7 minutes until browned and tender. Add the mustard and balsamic vinegar to the skillet. Stir well to combine.
Step 3
Cook the mushrooms for a minute or two more. They should be well coated in the flavorings and browned all over. Allow any liquid to reduce right down before serving.
Ingredients
Brown mushrooms (Italian or Crimini mushrooms), raw – 3 cup