Prep Your Dry Mix: In a large bowl, whisk together the sifted all-purpose flour, cornstarch, and kosher salt until fully combined. Set aside.
Cream Wet Ingredients: Using a stand mixer with a paddle attachment, beat the softened butter and granulated sugar together until the mixture is light and fluffy.
Add Flavor & Eggs: Mix in the vanilla extract, then add the eggs one at a time, ensuring each is fully incorporated before adding the next. Scrape down the sides of the bowl.
Form the Dough: Gradually add the dry flour mixture to the wet ingredients on low speed. Mix until just combined, being careful not to overmix.
Divide and Color: Divide the dough into two equal portions. Add a few drops of pink food coloring to one portion and mix until you achieve a lovely soft pink color.
Roll & Chill: Roll out both the plain and pink dough portions to about 1/4 inch thickness. For easy cleanup, roll them between two sheets of plastic wrap. Place each rolled dough sheet onto a baking sheet and chill in the refrigerator for at least 20 minutes until firm.
Add Sparkle (Optional): If you're using pink sanding sugar, sprinkle it evenly over the chilled pink dough. Gently roll over it with a rolling pin to press the sugar into the dough. Return to the fridge if it softens.
Cut Strips: Once firm, use a ruler and a sharp knife to cut 1/2-inch wide strips from both the plain and pink dough. Keep them cold.
Assemble Stripes: Carefully arrange the dough strips, alternating plain and pink, making sure they are touching side-by-side. Gently tap them together to adhere.
Seal the Stripes: Place a piece of plastic wrap or parchment paper over the striped dough. Gently roll over it one last time to help fuse the strips together. Chill again briefly.
Cut Shapes & Bake: Preheat your oven to 375°F (190°C). Use a heart-shaped cookie cutter to cut out your cookies from the striped dough. Place them carefully on a baking sheet lined with parchment paper or a silicone mat.
Bake to Perfection: Bake for approximately 12 minutes, or until the edges are lightly golden.
Cool & Enjoy: Let the cookies cool on the baking sheet for a few minutes before moving them to a wire rack to cool completely. Share these delightful treats!