Heat oven to 400 degrees. Lightly coat 12 well muffin pan with nonstick cooking spray. In bowl, combine muffin mix, buttermilk, egg and 2 tbsp butter until blended. Gently fold in the blueberries and pecans.
Spoon batter into prepared pan. Brush tops with 1 tbsp butter. Bake 12 minutes or till golden brown. Let cool 5 minutes, remove from pan.