Chocolate Thumbprint Cookies (Heart-Shaped)

In a small bowl, combine flour, salt, and cornstarch, whisk and set aside
In a medium bowl, beat the softened butter until smooth, then slowly add the powdered sugar, and continue beating until completely incorporated and smooth.
Add the egg yolk and vanilla extract and beat together until incorporated
With the mixer on low speed, slowly add the dry ingredients and beat until combined. The dough will seem crumbly but continue mixing until it comes together.
Roll cookie out into 12 equal sized balls and then press them down to form discs.
To achieve the heart shape, press index finger down onto the dough to form a heart-shape, or use the back of a small ¼ teaspoon (see image in post to know what you're looking for).
Refrigerate dough for at least 20 minutes or freeze for at least 10 minutes.

While dough is chilling, heat heavy cream in microwave for 30 to 45 seconds until hot, then pour oven chocolate chips. Let sit for a minute and then stir to combine until smooth. If the chocolate still has chunks, microwave for 15 second increments and stir until completely melted. Set aside and let cool for a few minutes.
Preheat oven to 350° F
Line a baking sheet with parchment paper and set aside
Remove cookies from fridge or freezer and place on baking sheet (at least 1.5 inches apart) and add a small amount of ganache to each heart cookie.
Place in oven and bake for 10-12 minutes or until the edges turn golden brown and the chocolate starts to bubble a little.
Remove from oven and allow to cool completely before serving.