Preparation

• 1. Preheat the oven to 300°F. Using a 2" cookie cutter (or any circular object of similar size), trace 12 circles on an 8 1/2” by 11” sheet of paper, leaving about 1" between the circles. Set aside; you'll use the paper later to help shape your cookies.
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  2. To make the meringue: Combine the cashews and cornstarch in a food processor. Pulse 8 to 10 times to make a coarse flour.
  3. Wipe the inside of your mixing bowl (or the bowl of your stand mixer) with vinegar or lemon juice. Coat the mixer’s whisk (or the whisk you’re using) with vinegar or lemon juice as well.
  4. Place the egg whites in the bowl and whisk them on low speed until foamy; delicate bubbles will appear on the surface.
  5. Add the cream of tartar and salt and continue to whisk the egg whites until soft peaks form, about 2 to 3 minutes.
  6. Increase the speed to high and slowly add the sugar a tablespoon at a time, whisking until stiff peaks form. The meringue should look glossy and stiff but not dry.
  7. Gently fold the ground nut mixture into the meringue, being careful not to deflate it.
  8. Place the paper you made as a guide on one side of a half-sheet (13” x 18”) pan. Put a full-sized piece of parchment on top; you should be able to see the traced circles through the parchment.
  9. Place a heaping tablespoon of meringue in the middle of each circle; a level tablespoon cookie scoop works well here. Alternatively, pipe the meringues using a 1/2” round tip.
  10. Once you’ve shaped 12 meringues, move the paper to the other side of the pan and repeat, making a total of 24. Using an offset spatula dipped in water, flatten the meringues to completely fill their circles.
  11. Repeat the process with a second pan and the remaining batter to shape a total of 48 meringues. Lightly tap the pans on the counter to knock out any large air bubbles.
  12. To bake the meringues: Place both pans in the oven and immediately reduce the heat to 275°F.
  13. Bake the meringues for 45 to 55 minutes, or until they feel dry to the touch.
  14. Turn the oven off, prop the door open a crack, and let the meringues cool completely in the oven.
  15. To make the buttercream: While the cookies cool, make the buttercream. Fill a small pot with at least 1 1/2” of water and set it on a burner over low heat. Once the water starts to steam, turn it down to a gentle simmer.
  16. In a clean heatproof bowl (or the clean bowl of your stand mixer), whisk together the egg yolks, sugar, vanilla, and salt. Place the bowl over the pot of simmering water.
  17. Heat the mixture to 155°F, use a rubber spatula to stir and scrape the sides of the bowl to prevent the egg yolks from scrambling. When ready the mixture should look thick and syrupy; the process should take about 5 to 8 minutes. If it seems it’s taking too long increase the heat slightly; but make sure not to let the simmering water come to a boil, which could cook the egg yolks.
  18. Remove the bowl from the heat and, using the whisk, beat the mixture until light and fluffy, about 1 minute.
  19. Continue whisking at medium speed as you add the butter one or two cubes at a time, stopping to scrape down the sides of the bowl as needed. The buttercream will become light, fluffy, and smooth. Refrigerate until the cookies have cooled completely.
  20. To assemble the cookies: Place the graham cracker crumbs in a small bowl. If necessary, pair the meringues so you’re using ones closest in size.
  21. Using an offset spatula, spread an even, thin layer of buttercream on the bottom of a meringue. Sandwich the buttercream with another meringue, then spread buttercream all over the outside of the sandwiched meringues, starting with the sides.
  22. Place the buttercream-coated cookie in the bowl of graham cracker crumbs and toss gently to cover with an even layer of crumbs. Transfer the finished cookie to a parchment-lined baking sheet and repeat with the remaining cookies.
  23. Freeze the cookies for at least 30 minutes, lightly covered, or until the buttercream has set. Serve chilled.