Preheat oven to 375 degrees F. Line a muffin tin with 12 paper liners.
In a large bowl beat butter and both sugars together until light and fluffy.
Beat in the egg until well incorporated.
In a separate bowl whisk together the flour, baking powder and salt.
Add the flour mixture and the milk alternately in 3 additions, mixing well after each addition.
Fill the liners ½ full.
Bake 18-20 minutes or until lightly golden and a toothpick inserted in the middle comes out clean.
Let rest in the pan 5 minutes, then transfer to a cooling rack to cool completely.
While cupcakes are cooling make the frosting:
Beat butter and ½ the icing sugar together until light. Add in the melted chocolate once it has cooled to room temp. Add in the remaining icing sugar and the cream. Beat 2-3 minutes until smooth and fluffy.
Frost cupcakes using an off-set spatula or piping bag fitted with a large star-tip.
Recipe by Chateau Elma at https://www.chateauelma.com/brown-sugar-cupcakes-dark-chocolate-frosting