Line two sheet pans with parchment paper.

In the bowl of a food processor, combine powdered sugar, almond flour, and ½ teaspoon of salt, and process on low speed, until extra fine. Sift almond flour mixture through a fine-mesh sieve into a large bowl.

In the bowl of a stand mixer fitted with a whisk attachment, or a large bowl and a hand mixer with the whisk attachment, beat egg whites and the remaining salt on medium high speed until soft peaks form, 4-5 minutes. Gradually add granulated sugar, 1 tablespoon at a time, until fully incorporated, 5-6 minutes. Continue to beat until stiff peaks form, 2-3 minutes more. Scrape down sides of bowl, add vanilla, and beat until incorporated, 30 seconds to a minute. Add about ⅓ of the dry ingredients to the egg whites and use a spatula to gently fold until just combined. Repeat until all dry ingredients are incorporated. Batter texture should be thick but pourable, meaning it falls in an unbroken ribbon when you lift the spatula from the batter. You should be able to draw a full figure 8 over the batter before it sinks. If batter breaks or figure 8 does not hold, continue gently folding and figure 8 testing until it does.

Transfer the macaron batter into a piping bag fitted with a medium round tip.

Place 4 small dots of the batter in each corner of rimmed baking sheet, and replace the piece of parchment paper over it. Batter will “glue” parchment to pan for easier piping of macarons. Pipe the macarons onto the parchment paper in 2-inch circles with 1 inch of space between. Tap each baking sheet on a flat surface 5 times to release any air bubbles.

Let the macarons sit at room temperature for 30 minutes to 1 hour, just until dry to the touch. Do not over-dry, or macarons may collapse during baking. Preheat the oven to 300˚F while they dry.

Note: fillings can be made during resting, baking, and cooling time.

As soon as they are dry to the touch, bake the macarons for 15-17 minutes, or until the feet are well-risen and tops are smooth and matte. Macarons should not brown at all during baking.

Immediately and carefully transfer the macarons to a wire rack to cool completely before filling.

Add chocolate to a medium mixing bowl.

In a small saucepan over medium heat, add cream and heat until scalded, 180°F-185°F. Pour cream over chocolate and cover for 5 minutes. (Alternatively, chocolate and cream can be microwaved at 30 second intervals, stirring in between, until melted and homogenous.)

Add vanilla and salt, and whisk until smooth. Refrigerate until firm.

Place egg whites and cream of tartar in the clean and dry bowl of a stand mixer, and set aside for later.

Place a candy thermometer on a medium saucepot over low heat. Add water, sugar, and corn syrup, and stir constantly until sugar is dissolved. Once dissolved, stop stirring and increase heat to medium. Heat until mixture is 200°F, about 5 minutes, and then begin whipping egg whites.

Whip egg whites on medium speed to soft peaks, about 5 minutes. At this point, the sugar syrup should be at or near its final temperature of 240°F. (If syrup reaches 240°F before egg whites are soft peaks, remove from heat; syrup can be reheated over low heat if it hardens before egg whites are ready.)

Once syrup is 240°F and egg whites are soft peaks, immediately remove syrup from heat. Turn mixer to low, and slowly stream syrup into egg whites, ensuring stream of syrup falls between the whisk and the sides of the bowl, directly into the egg whites. If sugar begins to harden while streaming, place back over low heat briefly until liquid again.

Once all sugar syrup has been added, increase speed to high and whip for 6-8 minutes, or until mixture is thick and glossy. Mixture may deflate slightly at first, but continue whipping on high until it rethickens.

Finally, add vanilla and whip until the fluff has cooled to room temperature, another 5 minutes or so.

Fill two large piping bags fitted with round tips with chocolate ganache and marshmallow fluff, respectively.

Turn half of the macarons over, foot-side up. Pipe about a tablespoon of each filling onto the flipped macarons. Place the remaining macarons on top of the filled ones to create sandwiches.

Macarons keep in an airtight container in the fridge for about 1 week.