Prep. Preheat oven to 350℉ (175℃). Grease or line 12 muffin cups with paper liners.
Mix dry ingredients. In a large bowl, whisk together the flour, baking powder, salt, and ground allspice.
Make batter. In a separate bowl, cream together the 1 cup sugar and shortening until light and fluffy. Beat in the eggs one at a time, then stir in the dry ingredients and milk alternately (a third of the dry ingredients, half the milk, a third of the dry ingredients, last half of milk, then the final third of dry ingredients). Stir in the sourdough starter by hand, scraping the bowl to make sure everything is incorporated.
Fill muffin cups. Divide the batter evenly among the prepared muffin cups, filling each about ¾ full.
Bake. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Prepare cinnamon sugar coating. In a bowl, melt the 2 sticks of butter. In a separate bowl, combine the remaining 1 ½ cups of sugar and the cinnamon.
Dip and roll. Dip the baked muffins in the melted butter, then roll in the cinnamon-sugar mixture to coat. Serve warm or at room temperature.