Preheat oven to 375F
Whisk flour, brown sugar, baking powder, baking soda, cinnamon and salt in a large bowl.
Using a fork, cut 3 ounces of chilled butter into dry ingredients.
In a small bowl whisk egg yolk, milk and molasses.
Mix wet ingredients into dry ingredients and stir until combined.
Turn dough onto floured work surface and knead until fully combined.
Roll into a 3/4″-1″ thick circle. Cut into 8 equal wedges.
Place on parchment lined baking sheet.
Bake 15-17 minutes.
Cool slightly on wire rack.
Whisk all icing ingredients in a bowl, and drizzle over cooled scones.