• For the caramelized apples: In a medium skillet set over medium heat, melt the butter, then whisk in the sugar. Add the apples, and sauté until soft and caramelized, about 10 minutes.
• Scoop ½ cup (125 ml) of the caramelized apples into the container of a blender. Add the heavy cream and blend to make a very smooth puree (you can also use a stick blender to do this.) Cool the puree completely.
• For the buttercream: Place the butter in the bowl of a stand mixer fitted with the paddle attachment, or in a large mixing bowl if using a hand mixer, and beat for a minute to soften. Add half the powdered sugar and beat on low speed to moisten the sugar, then increase the speed to incorporate fully. Add ¼ cup (60 ml) of the cooled caramelized apple puree, and beat to incorporate fully. Add the remaining powdered sugar, and beat on medium speed until the buttercream is smooth and fluffy.

  Transfer to a pastry bag fitted with a round tip and set aside until ready to assemble the macarons. (The buttercream can be made ahead; refrigerate, but make sure to return to room temperature at least an hour before using.)
• For the pecan macaron shells:

  *Return the egg whites to room temperature at least an hour before making the macarons shells.*

  In the bowl of a food processor, add the powdered sugar, almond flour, and pecans, and process until the mixture is thoroughly incorporated, 30 seconds to a minute. Sift the mixture through a fine-mesh strainer to make sure no lumps or bigger bits of nuts are left.
• In the bowl of a stand mixer fitted with the whisk attachment, or in a large stainless steel mixing bowl if using a hand mixer, whisk the egg whites on medium/high speed until frothy. Add a tablespoon of the granulated sugar, continue whisking at medium-low speed, then add the remaining sugar slowly. Increase the speed medium-high and whisk until the egg whites are bright white and create stiff peaks. At low speed, mix in a few drops of red gel food coloring, to your liking.
• Add the almond and powdered sugar mixture to the egg whites and, using a spatula, gently fold in the dry ingredients: slide your spatula all the way to the bottom of the bowl and comes back up to the top. Do this about 6 times to incorporate the dry ingredients, then keep folding for a total of about 14 times until no pockets of dry ingredients remain and the mixture drops from the side of the spatula in a slow, lazy ribbon. Start testing early to make sure not to overfold.
• Stack two baking sheets and line the top sheet with parchment paper. If you're not using parchment paper sheets, cut out the parchment paper so it fits exactly over the bottom of the sheet to make sure the macarons will lay flat. Slide macaron templates under the parchment paper, if using.
• Transfer the macaron batter in a pastry bag fitted with a ½-inch (1.25-cm) round tip. Pipe 1.5-inch (3.8-cm) rounds of batter, evenly spaced but still close to one another as they will not expand much.
• Carefully slide the macaron templates off the baking sheets, if you used them. Let the shells rest on the baking sheets for 20 to 30 minutes.
• Preheat the oven to 275°F (135°C) with a rack set to the middle position. Bake each sheet of macaron shells for 13 to 16 minutes, or until the shells are firm on their feet when you lightly tap on them with the tip of a finger.
• Let the shells cool completely to room temperature before assembling them, about an hour.
• To assemble the pecan macarons: Pair same sized shells together and set side by side on a work surface. Pipe some buttercream over half of the shells, following the circumference of each shell to create a circle of buttercream. Fill each circle with a small quantity of the saved diced caramelized apples. Close the pecan macarons, gently pressing the second shells over the filling.
• STORAGE: Store the assembled Apple and Pecan French Macarons in an airtight container and refrigerate overnight before indulging. French macarons will keep, refrigerated, for up to 3 days. You can also freeze assembled macarons in an airtight container for up to 1 month.
• SERVING: Always bring these Apple and Pecan French Macarons back to room temperature before serving.

NOTES

• This recipe makes about twice the amount of frosting you need to fill the macarons. Use the remaining frosting to garnish a cake or cupcakes, or freeze it in an airtight container until you make a new batch of macaron shells. Simply defrost to room temperature and whisk vigorously to soften before using.
• You will also have some of caramelized apple puree leftover (a tasty bonus!) Use this delicious treat like you would apple butter: spread over pancakes, croissants, or sliced baguette.