• Preheat the oven to 375 degrees F and line baking sheets with parchment paper.
• In a large bowl, add the butter and sugar.
• Using an electric mixer, beat on medium-high speed until very pale and fluffy (about 3 to 5 minutes).
• Add the egg and beat until well combined.
• Add in the egg yolk and vanilla extract and beat until combined.
• Add the flour, cornstarch, baking soda, and salt and beat on low until well combined.
• Divide dough into four bowls and add food coloring. Mix well with a fork.
• Chill dough for 30 minutes or more.
• Make golf ball-sized dough balls using 2-3 colors of dough for each cookie.
• Bake the cookies 8-12 minutes.
• Remove from the oven and allow to cool on the cookie sheet for 2 minutes
• Cool cookies on a baking rack.

Frosting Stitches

• Melt a small handful of chocolate melts in a piping bag according to the instructions on the bag.
• Snip the tip off the piping bag and use it to add stitches to the cookies.
• Follow the lines of different colors on the cookies.
• Allow to dry for 30 minutes.