Salted Caramel Macarons

=Ingredients=
==For the macaron shells:==
*150g (or ¾ cups) granulated sugar
*60ml (or ¼ cup) water
*60ml (or ¼ cup) egg whites, about 2 large egg whites
*150g (or 1½ cups) ground almonds or almond meal
*150g (or 1 cup + 3 tablespoons) powdered sugar
*60ml (or ¼ cup) egg whites, about 2 large egg whites
*a few drops of yellow food coloring, optional (only use gel food colorings for macarons!)
==For the whipped salted caramel filling:==
*175g (or ¾ cup + 2 tablespoons) granulated sugar
*60ml (or ¼ cup) water
*120ml (or ½ cup) heavy whipping cream
*175g (or ¾ cup + 1 teaspoon) unsalted butter, cubed
*sea salt to taste, I used about ½ teaspoon
=Directions=
===Start by making an Italian meringue for the macaron shells:===
#Please note: to make the Italian meringue, use the first three ingredients of the list of ingredients. In a medium-sized saucepan, combine the sugar and water. Heat over low heat, stirring until the sugar has dissolved. Once the sugar has dissolved, turn the heat to medium-high and allow the syrup to come to a boil.
#In the meantime, add the egg whites to a medium-sized, heatproof bowl and mix (with a mixer fitted with the whisk attachment) until foamy and the whites are almost able to hold soft peaks.
#Once the syrup is boiling, clip on a candy (or sugar) thermometer.
#Cook until the syrup reaches 116°C/240°F, then take the pan off the heat and slowly drizzle the hot syrup into the bowl with the foamy egg whites, mixing continuously to prevent the eggs from scrambling. Don't pour the syrup onto the whisk, or the syrup may splatter against the sides of the bowl (or into your face!). Instead, aim for a spot close to the whisk.
#Once all the syrup has been added, keep mixing until the bottom of the bowl feels cool to the touch and the meringue has cooled down to body temperature. If you want to use food coloring (I used a drop of yellow food coloring, but I don't think it made that much of a difference), add it and mix briefly until the meringue has a uniform color.
===Finish the shell batter:===
#Line two (or three, if you have them) large baking sheets with baking parchment. I always use a tiny dollop of italian meringue to stick the parchment to the baking sheet, This way, when I start piping, the parchment stays in place. Preheat the oven to 135°C/275°F (standard oven setting).
#In a large bowl, stir together the ground almonds, powdered sugar and remaining egg whites with a rubber spatula, until a paste forms.
#Using a rubber spatula, fold one third of the meringue into the almond paste. You don't have to be too careful with it just yet; this third of meringue is used to lighten the almond paste so that the remaining meringue can easily be incorporated without losing too much volume.
#Once you've lightened the paste with one third of the meringue, carefully fold in the remaining two third of meringue.
#The mixture is probably too stiff at this point, so stir with your rubber spatula until you come to the point where a ribbon of batter takes about 30 seconds to completely sink back into the bulk of the batter. At this point, the batter won't flow out of your piping bag or all over your baking sheets, and it won't be too stiff either.
#Plop the batter into a piping bag fitted with a large open tip and pipe 1½-cm (U.S. quarter-sized) dollops onto the prepared baking sheets. If you want shells of roughly the same size, do yourself a favor and make a template first. Slide it underneath the baking parchment to make piping the shells a little easier.
#Pipe 70-76 macaron shells. You probably need more sheets of baking parchment to pipe the shells on, even if you only have two baking sheets. Once all of the shells have been piped, allow them to sit undisturbed at room temperature for about 45 minutes to 1 hour. By drying the unbaked shells like this, you make sure that a skin forms on the outside of the shells.
#Once the unbaked shells have rested, bake for 20 minutes (one baking sheet at a time), or until you can easily pull a shell off the baking parchment.
#Allow the shells to cool to room temperature before filling them. You can also store the cooled shells in an airtight container for a day to make the shells extra delicious.
==Make the caramel filling once the macaron shells are resting or cooling==
#In a medium-sized saucepan (preferably a light-colored pan), combine the sugar and water. Heat over low heat, stirring with a metal spoon until the sugar has dissolved, then crank the heat up to medium-high. Allow to come to a boil.
#In the meantime, add the cream to a small saucepan and heat over low heat until the mixture reaches scalding point. Turn off the heat.
#Cook the sugar syrup until it turns into caramel. Once you're happy with the color of the caramel, take it off the heat and immediately whisk in the hot cream. The mixture will start to bubble and hiss like an angry snake (this is why the pan needs to be medium-sized) but just keep whisking and it will calm down.
#Add half the butter, one cube at a time, whisking until incorporated. Then plop the bottom of the pan in a cold water bath (fill your sink with an inch of cold water and dunk the bottom of the pan into it). Add the remaining butter and whisk until the caramel thickens (aka: cools).
#Transfer the caramel to a medium-sized bowl and place in the fridge or freezer to chill.
#Once chilled, use a mixer to whip up the caramel. Because there's a lot of butter in it, it will double in volume and lighten in color (like buttercream). Fold in sea salt flakes with a rubber spatula.
#Pair the macaron shells according to size and fill each pair with a teaspoon of the salted caramel filling.
#Store in an airtight container in the fridge, but serve at room temperature. The macarons are even better the next day!
Source: The Tough Cookie