Wash the lemon with hot water and dry it. Finely grate the peel and squeeze out the juice. Clean, wash and thinly slice the spring onions. Wash the rocket, shake dry and chop finely. Halve the avocados, peel and remove the stone.
Chop the pulp, finely puree with lemon juice and lemon zest, milk, quark and mustard. Stir in the spring onion slices and rocket and season everything with sea salt and pepper.