Preheat oven to 350°F. Line a 12-cup muffin pan with paper liners.
Beat the first 4 ingredients at medium speed with an electric mixer until well blended (about 5 minutes). Add the eggs, 1 at a time, beating well after each addition.
Whisk together the flour, baking powder, and salt in a medium bowl. In a small bowl stir together the milk and maple syrup. Add the flour mixture to the sugar mixture alternately with the milk mixture, beginning and ending with the flour mixture; mix after each addition.
Spoon the batter into the prepared muffin cups. Bake 20 minutes or until a wooden pick inserted in center comes out clean. Cool in the pan 10 minutes on a wire rack; remove from pan. Cool completely on wire rack.
FROSTING
Use an electric mixer to beat the maple syrup and next 4 ingredients (syrup through salt) in a large bowl. Gradually add the powdered sugar, beating just until blended (do not overbeat).
Spread the frosting over the cupcakes.
Notes
Double the frosting recipe if you want a generous smudge of frosting on each cupcake!