In a large bowl, mix together butter, powdered sugar, vanilla and egg until smooth paste forms. Sift in flour and baking powder then mix until a soft dough forms.
Divide dough into the number of colors you would like to use—we used orange, red and yellow. Tint each portion of dough with 3-4 drops of gel color then mix until incorporated. We left a few streaks in ours for a fun, marbling effect. Wrap each color of dough separately in plastic wrap and chill for at least 2 hours or overnight.
Remove dough from refrigerator then unwrap. Combine the colors into 1 large ball, or 2 separate color combinations, by kneading them together. (Be sure not to over-work the dough or combine the colors too much. The leaves look best when colors are distinct and don’t forget—you will need to collect the scraps and re-roll which will combine the colors even more.
Preheat oven to 350 degrees then line 2 cookie sheets with parchment paper. Roll dough out onto a lightly floured surface to ¼" thick. Use leaf-shaped cookie cutters to cut out shapes, dipping the cookie cutter into flour after each cut to ensure nice crisp edges.
Transfer cutouts onto the prepared baking sheets, spaced 1" apart, then bake 10–11 minutes—until the centers are barely firm to the touch. If the dough has a shiny look and is very soft, it has gotten too warm. Place the cut out cookies onto the cookie sheet and refrigerate for 5 minutes before baking.
Remove cookies from the oven and transfer to a cooling rack until they are completely cool. Meanwhile, stir together glaze ingredients then mix until smooth.
Brush each of the cooled cookies with a layer of glaze that is thick enough to add shine, but not so much that it runs off the sides. Return to cooling rack to let dry, then enjoy!
One Last Thing
For this particular recipe, we opted to use gel food colors because they’re more intense and let you use a lot less product—it also prevents you from having to add liquid to your dough, which can tamper with the consistency!