Chocolate Meringue Cookies

Position two racks in the upper and lower thirds of oven; preheat to 225°. Place 5 large egg whites in the bowl of a stand mixer fitted with a whisk attachment. Sprinkle ¼ tsp. cream of tartar and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt over egg whites and let sit for 5 minutes. Meanwhile, sift together ¾ cup (150 g) granulated sugar and ¾ cup (83 g) powdered sugar in a medium bowl and whisk to combine.

Beat egg white mixture on medium speed until foamy, 30–60 seconds. With motor running, add sugar mixture 1 Tbsp. at a time, incorporating completely before adding more and scraping down sides of bowl as needed between additions, 6–8 minutes total. Increase speed to high and beat meringue until glossy stiff peaks form (it should look billowy), about 2 minutes. (Stiff peaks are important here as the meringue will deflate slightly when piped; the cream of tartar will prevent overbeating). Reduce mixer speed to medium and add ½ tsp. vanilla extract, whipping just until incorporated.

Remove bowl from mixer. Sift in 1 Tbsp. (7 g) dark cocoa powder, such as Hershey’s Special Dark and gently fold it into the meringue until just incorporated. (Do not overmix. Some streaks are okay.)

Prepare a piping bag with a large straight tip, such as Ateco #809. Lower the piping bag into a tall glass or vase and fold the top of the bag over the rim of the glass to hold it in place. Fill the piping bag with meringue and twist the top of the bag to seal. Dab meringue in each corner of a baking sheet, then line with parchment paper using the meringue dabs as glue to hold the parchment paper down. Holding piping bag straight up about 1" about the baking sheet and moving in an upward motion, pipe meringues into 2" cookies on baking sheet, leaving an inch of space between each meringue. Repeat the process with a second baking sheet.

Bake meringues until crisp on the outside and shiny (but not sticky or tacky), 2 hours to 2 hours and 45 minutes. To check if they are ready, lift a meringue off the baking sheet: it should be light, lift off the baking sheet cleanly, and sound hollow when tapped on the bottom. If meringues are not done after 2 hours, keep baking, checking every 20 minutes. Turn off oven and leave door slightly ajar (prop open with a wooden spoon if needed). Let meringues cool in oven at least 1 hour and up to 12 hours.

Combine 12 oz. (about 2 cups) bittersweet chocolate chips and 2 tsp. refined coconut oil in a medium heatproof glass or metal bowl. Place bowl on top of a pot of simmering water over medium-low heat. (Make sure the bottom of the pot is not touching the boiling water.) Stir until the mixture is completely melted and smooth, 6–8 minutes. (Alternatively, place chocolate and oil in a microwave-safe bowl and microwave on high power in 15-second increments, stirring between each, until melted and smooth, 1 to 2 minutes total.)

Dip the bottom half of the meringues in the melted chocolate mixture, letting any excess drip back into the bowl. Set meringues on baking sheet to dry. Do ahead: Store meringues in an airtight container for up to 10 days.