1 stick unsalted butter, softened
1/4 c. sugar
1/4 c. light brown sugar
1/4 c. maple syrup
1 egg yolk
1/4 t. salt
1/4 t. cardamom
1 1/2 c. flour
maple syrup and sanding sugar for decoration
Cream butter and sugars in stand mixer until pale and fluffy, about 3 minutes. Reduce speed, add maple syrup, then egg yolk, beating well after each addition. In a small bowl, combine salt, cardamom, and flour. Add dry ingredients to wet all at once and beat until just combined. Form dough into a disk, wrap in plastic wrap and refrigerate at least 2 hours or overnight. (Dough will keep chilled up to 4 days.)
Preheat oven to 325F. Roll dough out on lightly floured surface to 1/4’’ thickness. Cut out cookies with maple leaf-shaped cutters and arrange on greased parchment on baking sheets. Use the tip of a paring knife or other sharp knife to draw the veins of the leaves onto the cookies.
Bake cookies in batches in the middle of the oven for 14-16 minutes. Remove parchment with cookies to cooling racks, and let cool 5 minutes. Brush with more maple syrup and sprinkle with sanding sugar.