Mushrooms stuffed with Tomatoes and Olives

Ingredients

• chopped walnuts
  ⅓ cup
• sun-dried tomatoes

  preferably organic (about 6 pieces)
  ½ oz
• all-purpose potato

  peeled and quartered
  1 small
• skim milk or soy milk
  3 tbsp
• to medium-size mushrooms (about 1 lb)

  stems removed and reserved
  36 small
• olive oil
  1 tbsp
• finely chopped onion
  1 cup
• garlic

  minced
  4 cloves
• crushed red pepper flakes

  or more to taste
  ⅛ tsp
• grated romano cheese

  optional
  2 tbsp
• chopped fresh flat-leaf parsley
  2 tbsp