Place the onions, the carrots, the bay leaf, the parsley, the white wine and a pinch of salt in a pot with water and boil them for 10 minutes.
Add the mackerel and let them boil for 15 minutes.
Take off the skin, remove any bones and flake the mackerel thoroughly. Set aside
Beat the eggs in a bowl and add the tomatoes, the cream, the fish and season to taste. Blend roughly to a finely chopped consistency.
Grease a baking pan with butter lined with aluminium foil (or another heat resistant paper) also greased with butter and pour the mixture into the pan.
Preheat the oven to 160ºC and place the pan in bain-marie.
Bake for 40 or 45 minutes.  To test the cake is cooked simply insert a skewer into the centre and check that it comes out clean.
Do not remove the cake from the pan until completely cold.
Serve with cocktail sauce or mayonnaise and decorate it with small bites of mango, avocado, cherry tomatoes and quisquillas from Motril (prawns).