1. Cut hake into small piece and boil in a saucepan for a minute. Drain.
2. In the same saucepan, cook the potato until tender.
3. Put olive in a frying pan to fry garlic and add parsley. Remove from heat and pan, add the fish broth, purée with immersion blender, and pass through a sieve.
4. In separate bowl, mix potato with fish and a tablespoon of oil. Blend everything with immersion blender until homogenous and smooth. Season.
5. Serve purée with sauce on top. Mix well on plate before eating so that the two mixtures are eaten together and the desired texture is achieved.