Something I threw together while making something else. I didn't have a recipe, just went with what seemed right. I was pretty happy (considering I had no recipe) that it came out good! :)
I used large white mushrooms (I had 8 at the time) with the stems removed, and reserved. Lightly salted the insides. Baked the caps empty-side-up, for about 20-25 minutes in a toaster oven on 325F, until they lost some of their moisture, but still held their shape.
For the filling, I finely chopped the following and put it in a small bowl:
1/2 celery rib
1 plum tomato
8 stems with the (picked side) ends cut off
To this I added one shredded baby carrot, 2-3 tablespoons of flavored breadcrumbs, one tablespoon (store bought) shredded Parmesan cheese, and about a tablespoon of melted butter. Mixed it well, and filled each mushroom cap evenly, and overfilled them with what was left.
I baked this in a toaster oven at 350F for about 30 minutes.
The result? Oh, they were delicious! And I will definitely be making these again. I didn't realize how easy this kind of treat could be. And because the filling would change depending on what ingredients I have handy, it would end up a little different every time. That would add some variety to my usual veggies. Maybe next time I can skip the butter and use a spray on salad dressing instead, or some butter flavored (non-stick) spray.