- With the rack in the middle position, preheat the oven to 200°F (100°C). Line a baking sheet with parchment paper.
- In a bowl placed over a pot of simmering water, heat the sugar, egg whites and cream of tartar, whisking constantly, until the sugar dissolves. Remove the bowl from the pot.
- Beat the egg white mixture with an electric mixer until completely cooled and stiff peaks form. With a spatula, gently fold in the chocolate and orange zest.
- Spoon the meringue into a pastry bag fitted with a plain round tip. Pipe tear-shaped (about 1 tbsp each) meringues on the prepared baking sheet. Dust with the cocoa powder.
- Bake for about 2 hours or until the meringues are dry and easily peel off the paper. Turn off the oven and let them dry for about 2 hours, leaving the oven door slightly ajar, using a wooden spoon. Let cool on the baking sheets.
- The meringues will keep for about 1 week in an airtight container at room temperature.
Enjoy these meringues plain or as part of a fruit fool, a dessert traditionally made with fresh fruit and whipped cream. For an Orange Fool, our riff on the classic old boy British dessert—Eton Mess—layer orange supremes with sweetened whipped cream and meringues in decorative glasses.