In a light-colored skillet over medium heat, cook butter until golden brown, stirring often. The butter solids will drop to the bottom of the skillet and turn dark brown. Remove from heat and pour through a fine sieve into heat-resistant bowl. Discard solids remaining in sieve. Chill brown butter until solid.
Heat oven to 400 F. Cover baking sheet with parchment , and dust lightly with flour.
In a medium bowl, sift together the flour, baking powder, baking soda, and salt.
Using a pastry blender or fingertips, blend cold brown butter into dry ingredients until no lumps larger than a small pea remain.
In a small bowl, whisk together syrup, buttermilk, egg, and maple extract. Add to dry ingredients and stir just until blended. You should be able to see a few wisps of flour. Don’t over mix!
Drop dough onto prepared baking sheet. With floured (or dampened) hands, press gently, shaping dough into a 3/4-inch thick disk. Sprinkle lightly with coarse sugar.
Use a sharp knife to cut into 8 equal wedges. Dough will be sticky – rinse knife between cuts. Be sure to press knife straight down and lift straight up.
Bake for approximately 18 minutes, until scones are light golden brown. Cool on rack for 10 minutes. Carefully separate scones.
Whisk together icing ingredients until smooth and drizzle over lukewarm scones.