In a large bowl, whisk together the flour, sugar, baking powder, salt, cinnamon and nutmeg. In a small bowl, lightly whisk the egg yolks, then whisk in the milk and 2 Tbs melted butter. Add the yolk mixture to the flour mixture and, using a wooden spoon, stir until well blended. The batter will be lumpy.
In a clean bowl, using an electric mixer on high speed, bet the egg whites until stiff, but not dry, peaks form. Using a silicone spatula, fold about ⅓ of the egg-whites into the batter to lighten it, the fold in the rest just until no white streaks remain. Use the batter right away.
Brush the wells of the ebelskiver pan with some of the remaining melted butter and place over medium heat. Working quickly, put ½ tsp of the brown sugar in each well followed by about 3 Tablespoons of batter ( I use an ice cream scoop, perfect size)
Cook until the bottoms of the pancakes are lightly browned and crisp about 2 minutes. Use a wooden skewer to turn the pancakes over in the pan and cook the other side for another 2 minutes.
Transfer the finished pancakes to the plate, and repeat to make two mare batches. Keep warm in oven until serving.