In a medium bowl sift together the gluten-free flour, unsweetened cocoa powder, baking soda, espresso powder, and kosher salt and set aside.

In the bowl of the stand mixer fitted with the paddle attachment, combine the room-temperature butter, granulated white sugar, and light brown sugar. On medium-high speed cream until smooth and creamy, about 3-4 minutes. Scrape down the sides of your bowl.

Add the room temperature egg, vanilla extract, and water and beat on high speed until combined, about 1 minute. Scrape down the sides and up the bottom of the bowl and mix to combine. It is possible the mixture will look curdled. No reason to worry.

Add the dry ingredients to the wet ingredients and mix on low speed until combined. The chocolate thumbprint dough will be thick.

Cover the mixing bowl and refrigerate for 15 minutes.

With a small cookie scoop divide the gluten-free chocolate cookie dough into 20-24 equal size portions.

Roll the cookie dough balls between the palms of your hands into smooth balls with no cracks.

Using a melon baller, a round teaspoon measuring spoon, the end of a wooden spoon or your thumb to indent each cookie.

Cover the indented chocolate dough and chill for at least 60 minutes (and up to 2 days) in the fridge.

When ready to bake the thumbprint cookies, preheat the oven to 350 degrees. Line two baking sheets with parchment paper.

Bake in the fully preheated oven for 9-11 minutes. The cookies will be puffy.

Remove the cookies from the oven and place the cookie sheet on a wire rack. With a cookie cutter or a glass scoot the cookies back into a perfect round shape and 'Re-Indent' the cookies.

Allow the cookies to cool for a few minutes on the sheet tray before transferring them to a cooling rack to cool completely.

Finely chop the dark chocolate and place it in a small bowl.

In a small saucepan bring the heavy cream to a gentle boil.

Carefully pour the hot heavy cream over the chopped chocolate. Allow for it to sit for a few minutes before carefully stirring it together.

With a small cookie scoop or spoon, fill each indent of the chocolate thumbprint cookies with the dark chocolate ganache.

Allow the ganache filling to set up before sprinkling it with some coarse sea salt, additional chopped chocolate or even sprinkles if you like.