Preheat the oven to 400 F. Line a standard 12 muffin tins with paper linings. Set aside.

In a large bowl, combine flour, baking powder, baking powder, salt and sugar. In a separate bowl, whisk together milk, egg, and melted, slightly cooled butter. Slowly add to the dry ingredients and stir until it’s only just combined.

To make the cinnamon mixture  - In a medium bowl, combine brown sugar, cinnamon and melted butter. Mix until all ingredients are combined. Add half cinnamon mixture to the batter and fold gently.

Divide the batter among the muffin tins using a cookie scoop. Top with the rest of the cinnamon mixture. Bake for 12-15 minutes or until a toothpick inserted in the center comes out dry.

Cool in the muffin tins for a few minutes, then transfer to a cooling rack.

To make the glaze, in a small bowl, whisk together powdered sugar and milk until smooth. Drizzle over warm muffins