400grams(14 ounces / 1 ¾ cups) caster (superfine) sugar(I use granulated, but weigh it in grams vs volume)
150grams(5 ½ ounces) honey
70grams(2 ½ ounces / 2 large) egg whites, at room temperature
110grams(3 ¾ ounces / ¾ cup) shelled pistachio nuts, lightly toasted, chopped(you may need a little extra)
2tablespoonsicing (confectioners’) sugar
Lightly spray a 9 by 13-inch baking tin with oil, line the base and two long sides with non-stick baking paper and lightly spray the paper with oil.
Combine 345 grams (12 ounces/1 ½ cups) of the sugar, the honey and 125 ml (4 fl oz/½ cup) water in a medium, deep heavy-based saucepan. Stir over low heat until the sugar dissolves. Bring to a boil and simmer, without stirring, until the syrup reaches 127°C (260°F) on a sugar thermometer (this is the upper end of the hard-ball stage). Watch it carefully, as the syrup has a tendency to bubble up.
Meanwhile, slowly sprinkle the gelatin over 160 ml (5 ¼ fl oz/⅔ cup) cold water in a shallow microwave-safe bowl and set aside for 5 minutes. Heat in the microwave for 30 to 45 seconds on High (100%), or until the gelatin has dissolved.
When the sugar syrup reaches 115°C (239°F), whisk the egg whites in an electric mixer with a whisk attachment on medium speed. When frothy, increase the speed to medium-high and gradually add the remaining sugar, whisking until thick and glossy. Keep the mixer running on medium speed.
When the sugar syrup reaches 127°C (260°F), turn off the heat and allow the bubbles to subside.
Increase the mixer speed to medium-high and gradually pour the gelatin mixture down the inside of the bowl in a thin, steady stream. Add the hot sugar syrup in the same manner. Increase the speed to high and continue whisking until the mixture is thick. Add the cardamom and whisk until the mixture is very thick and holds its shape, about 10 to 12 minutes, depending on your mixer. The outside of the bowl should almost be at room temperature.
Use the spatula to scrape the marshmallow mixture into the prepared tin and gently smooth the surface. Stand for 2 to 3 hours, until set.
Meanwhile, to make the coating, sift the icing sugar and cornflour together.
Dust the top of the marshmallow with some of the coating and turn out onto a clean surface. Dust the bottom with more coating. Use a large knife sprayed with oil to cut the marshmallow into pieces (if you cut 8 rows crosswise and 5 rows lengthwise you’ll have exactly 40 squares). Roll the sticky sides of each piece of marshmallow in the chopped nuts.