1. Line a loaf tin with plastic wrap, leaving it hanging over the sides. In a food processor, blend the raspberries (200g), icing sugar and water. Strain the purée into a bowl.
2. Using an electric mixer with a whisk attachment, beat the egg whites until stiff peaks form, then add the sugar and resume whisking back to stiff peaks - about 3-4 minutes.
3. Carefully fold the raspberry sauce and lemon zest into the whipped cream. Fold the cream into the egg whites with a metal spoon. Pour the mixture into the tin, fold the plastic wrap over to cover and freeze overnight.
4. Turn out the semifreddo, cut into slices and serve with the ginger biscuits and a bowl of raspberries.

To prepare Ginger Biscuits:

1. Preheat the oven to 180C. Grease and flour a baking sheet. Sift the dry ingredients together and add the sugar.
2. Melt the butter, add the golden syrup and combine with the dry ingredients to form a smooth dough.
3. Place tablespoonfuls or walnut-sized pieces of dough on the baking sheet about 5cm apart and flatten slightly. Bake until they are golden brown with crisp edges - 12-15 minutes. The centre will be slightly soft. Cool on a wire rack.