Melt butter in microwavable measuring cup. Set aside.
In small bowl, combine 1/3 cup sugar and cinnamon for topping. Set aside.
In large bowl, combine Bisquick, 1/3 cup sugar and nutmeg. In separate bowl mix together milk and eggs. Dip out 3 Tbsp. butter from melted butter, add to eggs and milk. Pour this over dry mixture, stirring only until combined. Stir in blueberries, if desired.
Spray 12-muffin tin with PAM.
Pour batter evenly into 12 muffin cups.
Bake at 375 for 15 minutes. Remove from oven, let pan cool on wire rack for about 3 minutes. Carefully remove muffins from pan, running a knife around the edge of each muffin to prevent crumbling. Dip each muffin top in remaining melted butter, then in cinnamon/sugar mixture. Serve warm.