Clean and scrape out mushrooms - careful to do this without breaking, but scrape out as much as possible
Pre-heat oven to 375 degrees
Sautee onions, peppers and celery in a little bit of olive oil
Add in clams with juice
You can also add a splash of white wine
Season with a little salt, pepper and garlic powder. Remove from heat.
Slowly mix in breadcrumbs, a little at time. You don't want too much, you really just want it to absorb the juice
Stuff mushrooms with filling
Melt butter and add some white wine in the skillet. Drizzle over mushrooms
Cover mushrooms with foil and bake for approx. 45 minutes.