1. Combine 275g caster sugar and 130ml water in a saucepan. Cook over medium-high heat until mixture reaches soft ball stage (about 118°C on a sugar thermometer; 3-5 minutes). At this point continue to cook while you do the following steps.

2. Meanwhile, squeeze water from gelatine and place in a heatproof bowl placed over another bowl of hot water until melted. Keep warm.

3. Whisk eggwhites in an electric mixer until soft peaks form, then gradually rain in the remaining sugar until incorporated and which until smooth and glossy.

4. Meanwhile, syrup needs to get to hard ball stage or 127°C on a sugar thermometer. Once it reaches this temperature, add the melted gelatine to sugar syrup, then, whisking whites mixture continuously, gradually add the syrup down the side of the bowl to prevent this from splashing it over the bowl. Add one-quarter of the raspberry powder and whisk until cooled and thick, about 10 minutes, then transfer to a deep, 20cm x 30cm tray lined with baking paper (see note), smooth top and set aside until set (3-4  hours).

5. When marshmallow is set, toss the sugar and raspberry powder in a bowl to combine. Turn marshmallow onto a sheet of baking paper and cut into squares (you can dust with a little sugar mixture to help with it sticking to the knife) and transfer to the bowl of sugar mixture and toss to coat. Marshmallows will keep for 1 week in an airtight container.