Stuffed Portabella Mushroom Caps

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4 medium portabella mushrooms (about 1 pound)
2 Tablespoons butter
1/2 cup chopped onion, small dice
2 cloves garlic, finely chopped
1/2 cup crumbled blue cheese (about 2 ounces)
1/3 cup chopped walnuts



Preheat oven to 400°F.
Remove portabella stems; trim and chop stems (makes about 2 cups).
In a skillet, over medium heat, heat butter.
Add onion, garlic and chopped mushroom stems; cook and stir until onion is soft and mushrooms are lightly browned, about 5 minutes.
Stir in cheese and walnuts.
On a shallow baking sheet, place portabella caps, stem side up. Divide mushroom-cheese mixture among portabellas.
Bake until mushrooms are tender, about 20 minutes.
Sprinkle with chopped parsley, if desired.

** I like to throw in a little lemon thyme along with the cheese and walnuts. Other fresh herbs are good too. I also like to brush the mushrooms inside and out with a mixture of 1Tbsp balsamic vinegar and 2 Tbsp extra virgin olive oil. These grill beautifully!