Preheat the oven to 400°F. Lightly grease a standard muffin pan; or line it with papers, and grease the papers.
In a medium-sized mixing bowl, whisk together the flour, baking powder, baking soda, salt, stollen spice, sugar, and the fruits and candied peel.
In a separate bowl, whisk together the egg, buttermilk or yogurt, and melted butter.
Quickly and gently combine the dry and wet ingredients; this should only take a few stirs with a bowl scraper or large spoon. The batter will be stiff.
Spoon the batter into the prepared pan, filling the cups about ¾ full.
Bake the muffins for 20 minutes, until a cake tester or toothpick inserted into the center of one muffin comes out clean.
Remove the pan from the oven, wait 5 minutes, then transfer the muffins to a rack.
Brush the tops of the muffins with the melted butter, then dust with sugar.
Serve warm or at room temperature.
