Leave the butter at room temperature before starting to bake. Mix the butter, sugar, and cornstarch until smooth and silky.
¾ cup Butter, 1 cup Granulated sugar, 1 tablespoon Cornstarch
Add the egg yolk and both extracts.
1 Egg yolk, 1 tablespoon Vanilla extract, ½ teaspoon Almond extract
Mix the flour and salt, add it in two or three passes, and mix well after each. You would have a soft and smooth dough in the end.
2¼ cup All-purpose flour, ¼ teaspoon Salt
Divide the batter into two equal parts and add 3 to 4 drops of Red Gel Food Colouring to half of the dough. Flatten the red dough into a rectangular shape and wrap it in cling wrap. Chill this dough for at least one hour. Keep the plain dough at room temperature. 3-4 drops Red gel food colour
After one hour, roll out the red dough into a rectangle with ¼ inch thickness. Use a medium-sized heart-shaped cookie cutter to cut the red hearts. Place them on a baking sheet and chill them in the freezer for 15 minutes.
When the hearts are hard enough to lift easily, wet your fingertip to stick them together and make a stack of red hearts. Place this stack in the fridge for 10 minutes.
The plain dough is at room temperature and soft. Cover and press all around the stach of hearts with the soft dough and gently roll this log on the counter to even out the plain dough.
Cover the log with cling wrap and chill it for two hours. Preheat the oven to 350F and line the baking sheet with parchment paper. Unwrap the log and cut it into half-inch slices. Place the slices on the baking sheet 2 inches apart, and bake them for 10 to 12 minutes. Cookies are done when their edges are set and slightly golden. Let them cool down on the baking sheet for 10 minutes, then transfer them to the cooling rack to cool down.