Line a sieve with a large piece of muslin. Pour in the yoghurt. Tie the muslin into a ‘parcel’ so that the yoghurt is contained. Squeeze out excess moisture. Place the sieve over a bowl and drain in the fridge for up to two days.
You will be left with a soft cheese. Mix through the zest and herbs. Roll into thumb-sized balls. Store in a glass jar in the fridge with the garlic, and cover with olive oil. It will keep for 7–10 days.