Step 1:
Preheat the oven to 190°C/375°F/Gas 5. Brush a 30 x 20cm tin Step 2:
with oil and line the base with non-stick baking parchment. Step 3:
Purée half of the raspberries in a food processor, reserving Step 4:
the other half. Mix the puréed raspberries with the egg yolks, Step 5:
caster sugar, yogurt and oil. Sift in the flour and cocoa and Step 6:
gently fold into the raspberry mixture. Step 7:
In a medium bowl, whisk the egg whites until they form soft Step 8:
peaks. Add a spoonful to the raspberry and chocolate mixture Step 9:
and stir well to loosen. Then gently fold in the rest of the egg Step 10:
whites and remaining raspberries. Step 11:
Spoon into the tin and bake for 20 minutes or until just firm Step 12:
to the touch. Cool for 5 minutes, then turn out onto a rack, Step 13:
removing the baking paper. Cut into squares to serve. Store Step 14:
in an airtight container. 