Line a large baking sheet with parchment paper and slide a printed-out macaron template underneath the paper on one side. Set aside.

Using a fine mesh sieve, sift the almond flour, powdered sugar and espresso powder into a large mixing bowl. Repeat the sifting 3 times in total. Set aside.

In the bowl of a stand mixer fitted with a whisk attachment (or in a large bowl with a handheld electric mixer), add the egg whites and cream of tartar and whip on Low speed for about 2 minute, until foamy.

Turn up the speed to Medium/High and continue to whip for 3-4 minutes, until soft peaks form.

Slowly, add the sugar, one spoon at a time, while continuing to whip for another 2-3 minutes, until the whites are thick and glossy and hold stiff peaks.

Fit a large piping bag with a large, round tip (.4 inch/ 9 ½ mm/ #1 nozzle) and place it standing up in a tall glass. Carefully fill with the macaron batter. Hover the piping tip about a ¼ inch (6 mm) above the center of each circle of the template and gently pipe to fill ⅔ of the circle. Do not pipe to fill the circle fully or your macarons will spread and bake into each out. Move the template to the other half of the pan and continue piping. Just fill 1 tray.

Once the batter is piped, bang the tray on the counter top to release air bubbles (rappe) and let the macarons rest until they are dry to the touch and have almost formed a skin, about 45-60 minutes depending on your climate. (This is a good time to make the Chocolate Caramel Filling below).

Toward the end of the resting time, preheat the oven to 300°F (150°C) and once the macarons are ready, bake for 17-20 minutes, until the feet are dry (and not sticky). Let cool completely.

Combine the chopped chocolate, butter and salt in a bowl. Set aside.

Add the sugar and water in a small, high-sided saucepan and cook over Low heat to dissolve the sugar. Then turn the heat to Medium and gently cook without stirring until the sugar turns a medium-dark amber and begins to smell slightly smoky, 6-7 minutes.

Immediately whisk in the cream. Stand back as the mixture bubbles furiously, then on Low stir for about a minute, until smooth and no lumps.

Remove from the heat and pour the caramel sauce over the chopped chocolate. Let this mixture sit for five minutes to allow the chocolate to melt, then carefully mix until smooth. Set aside on the counter to let cool and thicken to a pipeable consistency. (Pop in the fridge for a few minutes if needed to thicken it up for piping) Note: If it sets firm at any point it can be re-melted and cooled again.

Using an offset spatula, carefully release the macarons from the parchment. Turn half of the macarons over so that the bottoms are facing up.

Add the thickened filling to a large piping bag fitted with a round or star tip and pipe a generous amount onto the upturned shell. Sandwich the macarons with the empty shells.

Place the filled macarons in an airtight container and refrigerate overnight to mature before enjoying the next day for better flavor and texture. Remove from the fridge and sit at room temperature for 20 minutes before eating.

The assembled macarons can be held in the fridge for a week.