It angers me as a consumer, that I can't use fresh egg yolks because of the salmonella risk.
Whisk egg and vanilla sugar. Make vanilla sugar Jamie Oliver style by blitzing 1/2 kg sugar and 2 vanilla pods in your food processor. Sieve. Store in airtight container.
Pour in buttermilk and yoghurt, add lemon juice and the peel of 1/2 a lemon. Taste if you want more sugar or lemon Serve cold with muesli/ granola or add fresh strawberries.