In the bowl of a stand mixer fitted with the paddle attachment or in a bowl using a handheld electric mixer (or just mixing by hand), add the butter. Mix until smooth, about 1-2 minutes. Add the powdered sugar, cocoa powder, salt, egg yolk and mix to combine. Add the gluten-free flour and mix for 2-3 minutes until the dough comes together.

Crumble the mixture over the bottom of the tart pan. Press evenly up the sides and into the bottom of the pan.

Bake the crust for 18-20 minutes. Remove from the oven and let cool.

Place the crust in the freezer before you start making the caramel. (It should be frozen for 20-30 minutes before adding the caramel.) I find the crust holds up better when it’s cold when you add the hot caramel. Note: You’ll want to remove it from the freezer and have it ready to go just before the caramel is up to temperature so you can pour the caramel into the cookie crust immediately after it reaches 238F.

Melt the sugar, butter, corn syrup, and salt together in a large, heavy-bottomed pot over medium heat. (A stainless steel pot works best for this caramel.)

Once the mixture comes to a boil, add the evaporated milk a little at a time, taking 5 minutes to add the milk.

Once all the milk is added use a candy thermometer and bring the mixture to 238F-240F and not any hotter! Even a few degrees hotter will make them chewy instead of soft. (This will take another 15 minutes or so!) I highly recommend double checking the temperature with an instant read thermometer as it comes to temperature.

Immediately pour the caramel into the prepared crust.

Refrigerate until the caramel is set and no longer warm, 1-2 hours.

For the ganache, place the chocolate in a small or medium bowl. Heat the cream (in the microwave or on the stove) until simmering. Pour the cream over the chocolate. Let the mixture sit for 1-2 minutes. Stir to combine until the chocolate is glossy and smooth. Spread the ganache evenly over the caramel. Chill until the chocolate is set and is no longer melty/soft. Sprinkle the tart with flaky salt.

Keep refrigerated until serving. For neat, even slices, I run my long chef’s knife under hot water, wipe dry and slice (repeating as needed to get clean slices). Enjoy!