Step by step

1. Chop the chocolate in smaller pieces and melt it using the bain-marie method (double boiler).

2. Place the egg whites in a bowl of a stand mixer fitted with Mixer Whisk. Add salt and whip on speed 10 till soft peaks form. Gradually add caster sugar and continue whipping till glossy and stiff peaks form. Fit the stand mixer with the Flex Egde Beater Attachment and add vinegar and cornstarch. Mix on 1/2 stir speed to incorporate.

3. Slowly start adding the melted chocolate to the bowl. Mix till just incorporated.

4. Using a small ice cream scoop, scoop the mixture onto a baking tray lined with the parchment paper. Dust the cookies with cocoa powder. Bake in a 100°C preheated oven for 40 minutes. Let cool off completely in the oven.