The gills of the mushroom are quite bitter and as they cook will release an unpleasant looking black liquid. Use the tip of a butter knife, or a small spoon to gently scrape them out and discard.
In a small dish combine 2 Tbsp oil and ½ of the garlic. Brush this mixture inside the mushroom caps and place on a baking sheet. Sprinkle with salt and pepper and bake at 450°F for 10 minutes, or until just tender.
In a small dish mix together the breadcrumbs and the cheese. Set aside.
In a medium bowl, mix together the remaining ingredients and spoon into the mushroom caps. Top with the breadcrumb mixture and bake for another 10 minutes or until the breadcrumbs are golden and the filling is hot.