Preheat oven to 400 degrees.
Prepare a large baking sheet with parchment paper or spray a baking sheet with non-stick spray.
In a skillet, over medium heat, melt the unsalted butter.
Add the shallots and red pepper. Saute for about 4 minutes. Onions become translucent and red pepper softens.
Add the minced garlic for another minute.
Remove from heat and let cool.
While onion/red pepper mix cools, clean the mushrooms. Wipe mushrooms with a paper towel. Remove the stems from the mushrooms and discard.
In a bowl, combine the cooled onion/red pepper mix, add the softened low-fat cream cheese, Old Bay Seasoning, salt, and pepper - to taste. Mix well.
Place about a teaspoonful of the mixture into each mushroom head. Place onto the prepared baking sheet.
Continue until all mushrooms are full.
Optional: Combine the Panko breadcrumb and melted butter and brush onto the tops of the mushrooms.
Bake in the oven for about 15 minutes. Mushrooms will be golden brown.