Preheat oven to 375°F. Line a jelly roll pan or baking pan with foil and place a cooling rack in the pan.

Rinse mushrooms and pat dry. Carefully remove the stems, then chop the stems finely and set aside.

Melt butter in a skillet over medium-low heat. Brush each mushroom cap lightly with a bit of melted butter and arrange them, rounded side down, on the rack.

Add the chopped mushroom stems, onion, and bell pepper to the remaining butter in the skillet. Cook, stirring occasionally, until the onion is tender and translucent.

Stir in the parsley, chopped bacon, lemon juice, drained clams, and bread crumbs. Blend well and remove from heat.

In a separate bowl, lightly beat the egg. Once the stuffing mixture has cooled slightly, add it to the egg and stir until well combined.

Spoon the stuffing mixture into each mushroom cap, mounding it slightly. Sprinkle the tops with grated Parmesan cheese.

Bake for 20 to 25 minutes, or until the mushrooms are tender and the tops are nicely browned.

Serve warm and enjoy!