Dark Chocolate Thumbprint Cookies

Preheat oven to 350F and line a baking sheet with parchment paper.
In a medium-sized bowl, whisk together the flour, dark cocoa powder, cornstarch, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or a large bowl if using a handheld mixer, beat the butter and cream cheese together on medium-high speed until smooth and no lumps remain.
Add the granulated sugar and beat on medium-high speed until combined, about 2 minutes. Scrape down the bottom and sides of the bowl.
Add the egg, egg yolk, and vanilla extract, and mix on low-medium speed until combined, scraping down the bottom and sides of the bowl as necessary.
Add the dry ingredients and mix on low speed until a dough forms. It will be thick and sticky, so you will need a cookie scoop otherwise the dough will stick to your hands.
Using a medium-sized cookie scoop (mine was a 1.125 oz cookie scoop), about 2-2.5 tablespoons of dough, scoop the cookie dough and place on the baking sheet 2-3 inches apart.
Bake the cookies for 11-12 minutes until the cookies are set. Remove the cookies from the oven and let cool for 2 minutes on the pan. Then, using a rounded teaspoon, press the bottom of the teaspoon into each cookie until it forms a rounded indent. You can also use your thumb.
Let the cookies cool on the baking sheet for an additional 5 minutes, then transfer to a cooling rack to cool completely.

While the cookies are cooling, make your ganache. Chop your chocolate finely and set aside.
Warm the heavy cream over the stove on medium heat until gently simmering and bubbles form at the edges of the pan. Pour the warmed heavy cream over the chopped chocolate and let sit for 3-4 minutes. The warmed heavy cream will melt the chocolate.
Gently stir the cream and chocolate together until completely combined and smooth.
Carefully spoon the ganache into the indents you made in the cookies. Top with shaved chocolate, mini chocolate chips, etc., and enjoy!