01 -
Whisk the flour, baking powder, and salt in a medium bowl until evenly combined.
02 -
Beat the butter and sugar with a mixer on medium speed for 2-3 minutes until lighter and creamy. Beat in the egg and vanilla, then mix in the dry ingredients on low just until a soft dough forms.
03 -
Divide the dough into three equal portions. Leave one plain, tint one red, and tint one green with gel food coloring. Flatten each into a rectangle, wrap, and chill for 30-45 minutes.
04 -
Roll each dough portion between parchment into a rectangle about 1/8 inch thick. Stack the green, plain, and red layers, trimming one short edge straight. Lightly roll over the stack so the layers adhere.
05 -
Starting at the trimmed short edge, roll the dough into a tight log, peeling away the parchment as you go. Roll the outside in sprinkles, wrap tightly, and chill for at least 2 hours until firm.
06 -
Heat the oven to 350°F (175°C) and line baking sheets with parchment. Slice the chilled log into 1/4-inch rounds and place them 2 inches apart.
07 -
Bake for 10-12 minutes, until the tops look set and the bottoms are just lightly golden. Cool on the pan for 5 minutes, then move to a rack to cool completely.