01 -
Preheat oven to 375°F/190°C. Line muffin pan with paper liners or grease well with cooking spray.
02 -
Whisk together flour, baking powder, and salt (if using unsalted butter) in a medium bowl.
03 -
In large bowl, mix sugar, eggs, and melted butter. Whisk in milk, rum, and vanilla until pale.
04 -
Gradually fold dry ingredients into wet until just combined. Stir in butterscotch chips. Batter will be thick and lumpy.
05 -
Fill muffin cups with 4 tablespoons batter each. Top with extra chips and sugar if desired. Bake 20-24 minutes until toothpick comes out mostly clean.
06 -
Cool in pan 5-10 minutes, then transfer to wire rack. Serve warm or at room temperature, optionally brushed with melted butter.