1 Preheat an oven to 160 degrees Celsius, fan, or equivalent. Grease and line two large baking trays with parchment paper.

2 In a spotlessly clean mixing bowl, use an electric whisk to beat the egg whites and salt to a soft peak consistency. Gradually spoon in the caster sugar as you continue whisking for five minutes until the mixture is glossy and smooth (and holds stiff peaks).

3 Lightly fold in the cocoa powder and ground almonds in two batches.

4 Transfer the mixture to a piping bag. Cut a 1.5cm width across the tip of the piping bag. Holding the piping bag perpendicular to the lined baking tray, pipe rows of 3cm diameter discs, leaving space between each disc. Smooth the surface of each disc with a damp finger.

5 Leave the piped macarons to stand for 20 minutes.

6 Meanwhile, make the filling by whisking the cream and icing sugar together until thickened, then add the lime zest.

7 Bake the macarons in the preheated oven for 20 minutes. Once baked, remove from the oven and leave for a few minutes before peeling macarons from the paper and transferring them to a wire rack to cool completely.