Instructions

1. Whisk the flour, baking powder, and salt in a medium bowl. Set aside.
2. In a large bowl, beat the softened butter and granulated sugar with a hand mixer on medium speed until light and fluffy, about 2 to 3 minutes. Beat in the egg, vanilla, and almond extract until combined.
3. Add the dry ingredients in two additions, mixing on low just until a soft dough forms and no dry streaks remain. Do not overmix.
4. Divide dough into two disks, wrap each in plastic, and chill until firm, at least 1 hour and up to 3 days.
5. Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper. On a lightly floured surface or between parchment, roll one dough disk to 1/4 inch thick.
6. Cut out shapes with cookie cutters, transferring them to prepared sheets, spacing about 1 inch apart. Chill the trays for 10 minutes to help cookies keep their shape.
7. Bake 9 to 11 minutes, until edges look set and bottoms are pale golden. Rotate pans halfway through. Cool on the sheet 5 minutes, then transfer to a rack to cool completely.
8. For the icing, whisk powdered sugar, 2 tablespoons milk, corn syrup, and vanilla until smooth. Adjust with drops of milk to reach thick toothpaste consistency for outlining; thin a portion to shampoo-like consistency for flooding.
9. Tint icing with gel colors. Pipe outlines on cool cookies, then flood inside the lines. Use a toothpick to nudge icing into corners and pop any bubbles.
10. Decorate with sprinkles immediately, or add wet-on-wet dots and lines for marbling. Let cookies dry at room temperature until the surface is set, 8 to 12 hours.