Fry the onions and leeks in the olive oil and butter for about 5 minutes, season generously with salt and pepper and cook until soft but not browned, then add the diced potato and enough water to cover the potatoes by an inch. Bring to a simmer, cover and cook for 10-12 minutes, then remove the lid and continue cooking until tender.
Once tender, add the kale and chicken stock cube and continue cooking until the kale is soft, then lightly break up the potatoes with a potato masher (this helps thicken the soup without using flour). Add more water if too dry, but you want this quite thick.
While the potatoes are cooking, place the smoked haddock in another pan with the milk, bay leaves and simmer for about 8 minutes until cooked through. Season with lots of black pepper. Halfway through cooking add the mussels and cover with a lid.
Once the fish is cooked through and the mussels are opened (if using fresh), remove the fish and pour the milk juices and mussels into the pan with the potatoes and simmer to warm through (if it's too watery, leave to simmer for a few minutes or too thick, add a splash of hot water).
Finally, remove the skin from the smoked haddock (if still on) and flake over the top of the chowder, garnish with a sprinkling of fresh parsley and a small squeeze of lemon juice (literally a teaspoon of juice) and serve with your choice of bread and enjoy!
Flexitarian Option
I often use pre-cooked mussels vacuum sealed for convenience, but you can leave out the shellfish altogether or swap for prawns, clams, whatever your preference.
Notes
I often use pre-cooked mussels vacuum sealed for convenience, but you can leave out the shellfish altogether or swap for prawns, clams, whatever your preference.