FOR MACARONS:
Step 1: Prepare Your Equipment
Wipe down the mixing bowl, whisk, and spatula with white vinegar or lemon juice to remove any grease or residue that could prevent the egg whites from whipping properly. Line your baking sheets with parchment paper.

Step 2: Grind and Sift the Dry Ingredients
In a food processor, combine the confectioners' sugar and almond flour. Pulse until the mixture is uniform in color. Sift through a medium-mesh sieve into a large bowl, discarding any lumps. 

 Step 3: Make the Meringue
Add the room-temperature egg whites to the stand mixer bowl and beat on medium-low until foamy. Add the cream of tartar, then slowly add the granulated sugar. Once soft peaks form, add the food coloring (if desired) and vanilla extract, then continue beating until stiff peaks form. The meringue must be stiff; you'll notice it filling the whisk as it nears the right stage.

Step 4: Macaronage
Gently fold in one-third of the dry ingredients into the meringue. Gradually add the remaining dry ingredients, folding gently each time. Use the spatula to carefully press the batter against the bowl to remove some air bubbles, but not too many. The final mixture should resemble flowing lava and be able to form a figure-eight pattern without breaking. Spoon the mixture into a piping bag fitted with a medium round tip.

Step 5: Pipe the Macarons
Pipe one-inch rounds onto a parchment-lined baking sheet (secured with a small dab of batter in each corner). Ensure the piping tip is perpendicular to the baking sheet; angling it may result in misshapen macarons. Tap the baking sheet on the counter several times to release air bubbles. Use a toothpick or skewer to pop any remaining bubbles on the surface.

Step 6: Let the Shells Form a Skin
Let the piped macarons sit for about 40 minutes before baking. This allows the shells to develop a skin, which is crucial for forming the iconic "feet" on the macarons. The shells should feel dry and not sticky to the touch before baking. Preheat the oven to 300°F (150°C) during this step.

Step 7: Bake and Cool
Bake the macarons for 12-15 minutes, rotating the tray halfway through (around 7 minutes). To check for doneness, gently try to wiggle the top of one macaron—there should be no movement, and the top should feel firm. Let the macarons cool completely before removing them from the baking sheet. For best results, bake one tray at a time.

FOR FRENCH BUTTERCREAM FILLING:
1. In a medium saucepan, combine the sugar and water, and gently heat over low, stirring until the sugar completely dissolves. Turn the heat to medium-high and bring the mixture to a boil.

2. While the syrup is heating, whisk the egg yolks in a stand mixer fitted with a whisk attachment until they become thick and foamy.

3. Once the sugar syrup reaches 240°F (115°C), remove it from the heat. With the mixer running, gradually pour the hot syrup into the egg yolks in a slow, steady stream.

4. Continue whisking until the yolk mixture cools to room temperature and the bottom of the bowl no longer feels warm.

5. Add the softened butter, one cube at a time, ensuring each piece is fully incorporated before adding the next. Mix in the vanilla extract, Pumpkin Spice Emulsion, and salt, beating until the buttercream is smooth and creamy, about 5-6 minutes. Add food coloring if desired.

FOR ASSEMBLY:
Pipe the buttercream onto the flat side of half the macaron shells, then sandwich them with the remaining shells. For the best results, store the macarons in the fridge for 1-3 days to allow the filling to soften the shells.