3 lb. button mushrooms (about two dozen)
1/2 sweet onion
3 cloves garlic
1 1/2 Tbsp. butter
1 Tbsp. olive oil
1 tsp. salt
4 oz. cream cheese, room temperature
3 Tbsp. grated parmesan cheese
First I wiped any dirt from the mushrooms and removed their stems. I also cleaned out the underside of the caps a little (basically maximizing room for filling!). I trimmed the hard, dry bases of the stems off, then chopped them finely. I also finely chopped half of a sweet onion and minced three cloves of garlic. I heated the butter and oil in a nonstick skillet over medium, medium-low heat. Then I added the onions, mushrooms, and salt and let them soften and cook down (probably 8-10 minutes), stirring occasionally. I didn't allow them to brown too much. Then I added the minced garlic, stirred, and allowed it to cook for another minute. Once the mushroom mixture was cooked, I took the skillet off of the heat and allowed it to cool slightly.
I put the softened cream cheese in a mixing bowl and added the parmesan cheese. I mixed it with a fork to combine, then added in the mushroom mixture. I put the cleaned mushrooms on a baking sheet, then filled the cavities with the cream cheese mixture. I baked the mushrooms at 400 degrees for about 15-20 minutes. The mushrooms will give off liquid as they cook, this is normal. Once the mushrooms were slightly shrivelled and no longer so liquidy, I removed them from the oven and transferred them to my serving platter.
These mushrooms could be varied endlessly to suit your tastes. Next time I might start by cooking bacon, then sauteeing the mushrooms and onions in the fat and adding the meat back in before baking. Maybe feta and sun-dried tomatoes? Bleu cheese and dried cherries? I see many mushrooms in my future . . . Be creative and enjoy!