Choose a new cookbook worth up to £28 when you subscribe to our magazine.
Dissolve the sugar in a medium saucepan with 120ml boiling water. When clear, bring to the boil and place a sugar thermometer in the pan.
Meanwhile, whisk the yolks with an electric mixer until creamy. When the sugar syrup reaches 120C, remove from the heat at once. Keep the mixer beaters running, drizzle the syrup onto the yolks and beat, on full speed, for 3-5 mins until you have a firm yellow foam. Remove and cool, whisking occasionally. Divide into 3 portions.
Use a third of this mixture for one mousse recipe, then chill and use the rest within 2 days or freeze in 2 portions for up to 2 months. To use the frozen mixture, thaw for 10-15 mins, then beat lightly until softened.