Line baking sheets with parchment paper or silicone mats.

In a medium bowl, whisk together the flour, cocoa powder, salt, baking powder, and cornstarch. Set aside.

In a large mixing bowl, beat the butter and brown sugar on medium speed until light and fluffy, about 1–2 minutes.

Beat in the egg and egg yolk for 30 seconds, scraping down the sides as needed.

Gradually add the dry mixture to the wet ingredients, mixing on low speed until just combined. The dough will be very thick.

Scoop 1 tablespoon of dough (use a #60 cookie scoop) and roll into smooth balls. Roll each ball in granulated sugar and place 2 inches apart on prepared baking sheets.

Use the back of a teaspoon to press a divot into the center of each cookie before baking. Place the baking sheet in the freezer for 10 minutes to firm up the dough. You can freeze longer if needed.

Preheat the oven to 350°F (177°C). Bake for 10-11 minutes or until the edges are set but the centers still look soft. Remove from the oven and immediately use the teaspoon again to gently deepen the center indentation as it disappears while baking.

Allow cookies to cool completely before filling.

Place the chocolate chips in a bowl. In a separate microwave-safe measuring cup, microwave the heavy whipping cream for 45 to 60 seconds, or until steaming and very hot. Pour the cream over the chocolate chips and let it sit for 2 to 3 minutes. Add in the almond extract, optional, and stir until the chocolate is fully melted and the ganache is smooth. Let the ganache cool for 10 to 15 minutes, or until it thickens slightly but is still spoonable.

Spoon about 1 teaspoon of ganache into the center of each cookie. Immediately add a maraschino cherry to each so they stick to the warm ganache. Let the cookies sit until the ganache sets.