Double vanilla macarons

Preheat oven to 180°C. Put eggwhites in a bowl and lightly whisk. Cover with plastic wrap and refrigerate overnight. Sift almond meal and icing sugar into a large bowl. Halve 1 of the vanilla beans, scrape seeds and add to almond meal mixture. Reserve bean. Draw forty 3.5cm circles on an A3 sheet of baking paper, with a 2cm gap between each. Set aside.

Pour 1⁄2 of the eggwhite into almond mixture without stirring.

To make meringue, put remaining eggwhite and cream of tartar in the bowl of an electric mixer. Put caster sugar and water in a small saucepan over a high heat. Cook until syrup reaches 112°C on a sugar thermometer, then start beating eggwhite mixture on medium, using the whisk attachment. When syrup reaches 118°C, pour into mixer with motor still running and beat until warm, but not hot.

Put circle paper on a large oven tray and top with a piece of baking paper. Spoon meringue into almond meal mixture and stir until smooth. Spoon batter into a piping bag fitted with a 1cm nozzle and pipe into the circles. Remove circle paper. Repeat with 3 more large oven trays to make 144 meringues, or until all batter is used.

Tap trays to flatten meringues, then set aside for 45 minutes or until a skin forms on surface of each. Bake 2 trays of meringues for 8 minutes then open door to release steam. Bake for a further 3 minutes, then open the door again. Bake for a final 3 minutes or until shells are risen and crisp. Transfer to a wire rack to cool. Repeat with remaining trays.

Put cream in a small saucepan. Halve remaining vanilla beans and scrape seeds. Add beans and seeds, and reserved bean, to cream. Put pan over a high heat and bring to the boil. Remove and discard beans. Put chocolate in a heatproof bowl and add hot cream mixture, a little at a time, whisking until mixture is smooth. Refrigerate for 30 minutes or until completely cooled.

Spoon chocolate mixture into a piping bag fitted with a 1cm nozzle and pipe a small amount onto 1⁄2 of the shells. Top with remaining shells. Serve.