Preheat oven to 375 degrees. Lightly grease baking sheet with nonstick cooking spray.

Gently clean mushrooms with damp cloth. Carefully separate mushroom caps from stems by holding caps & twisting off stems. Reserve stems & set caps aside.

For filling, in food processor or blender, combine mushroom stems, parsley, basil, garlic, onion powder, & ham. Process using pulse until finely chopped. Transfer to medium bowl. Stir in bread crumbs, lemon juice, olive oil, & pepper until well blended.

Place mushroom caps upside down on prepared baking sheet. Using teaspoon, carefully stuff caps with filling. Bake until heated through, about 15 minutes. Serve immediately.

This makes more stuffing than needed, so you could get extra mushrooms to stuff or bake the extra stuffing in a ramekin to eat on the side. Or whatever creative way you wish.