Preheat oven to 425 degrees. Spray a baking sheet lightly with non stick spray.
Remove stems from the mushrooms. (Reserve the stems.) Place the mushroom caps rounded side down onto the baking sheet. Lightly brush each mushroom cap with melted butter. Set aside.
Finely chop the mushroom stems. Place them in a skillet with the chopped pecans and heat over medium. Stir and cook until the mushrooms cook down and excess moisture is gone. (Do not add any oil or liquid to the pan.) Stir frequently to prevent burning.
In a large bowl combine the mushroom and pecan mixture with the cream cheese, ½ cup of the cheddar cheese, and the rest of the ingredients. Combine well.
Stuff each mushroom cap with the stuffing mixture. Top each stuffed mushroom with the remaining cheddar cheese.