Melt the butter in a large pot over medium heat, then add a drizzle of extra virgin olive oil. Add the diced smoked streaky bacon and cook until the fat has browned. Stir in the onion and leek, allowing them to sweat down before adding a pinch of salt. Add the celery and cook until softened.
Stir in the diced potatoes, pour in the white wine, and bring to a boil. Add the chicken stock and cream, then bring to the boil again before reducing to a simmer. Cook until the potatoes are tender.
Meanwhile, heat a griddle pan over medium heat. Drizzle the sourdough slices with extra virgin olive oil and toast them on the pan until golden and crisp.
Add the diced white fish to the chowder, followed by the mussels. Once the mussels open, they’re ready. Stir gently until the fish turns from pinkish-opaque to white and fully cooked.
Season with black pepper, add the scallops, and stir for 30 seconds until just cooked. Remove from heat and stir through the chopped chives, dill, and parsley.
Ladle the chowder into bowls and serve with toasted sourdough on the side.
