2. Gently mix a few spoonful of the yoghurt mixture with the egg whites, then slowly add the remainder of the egg white, trying to keep the airiness.
3. Fill 1/3 of the mixture in a cake tin lined with baking paper, layer with half the raspberries, then add the remaining mixture and top off with the remaining raspberries.
4. Put in the freezer to freeze.
5. Before serving, dip the bottom of the mould in hot water, turn the semifreddo onto a plate. Garnish with pistachios and raspberries.