Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.

Gently clean mushroom caps with a damp paper towel. Twist off the stems. Finely chop half the stems and set aside.

In a small skillet, melt 1 tablespoon of butter over medium heat. Sauté the chopped mushroom stems and minced garlic for 3-4 minutes until softened and fragrant. Let cool slightly.

In a medium bowl, mix the softened cream cheese, Parmesan, cooked stem/garlic mixture, green onions, and lemon juice until combined.

Gently fold in the lump crab meat, being careful not to break it up. Season with salt and pepper to taste.

Brush the mushroom caps all over with the remaining melted butter and arrange them on the baking sheet.

Fill each mushroom cap generously with the crab mixture, mounding it slightly.

In a small bowl, toss the panko breadcrumbs with a pinch of salt. Sprinkle the panko over the stuffed mushrooms.

Bake for 18-20 minutes, or until the filling is hot and bubbly and the topping is golden brown.

Let cool for a few minutes before serving, as the filling will be very hot.