Make the dressing by combining mayonnaise, celery, white wine vinegar, and onion powder, and ½ teaspoon Old Bay seasoning. Set aside.

Add the olive oil to a large skillet and place over a medium heat. Add the seafood mix and the remaining ½ teaspoon Old Bay seasoning. Cook until any pre-cooked seafood (eg mussels and shrimp) are warmed through, and the raw seafood (eg the calamari) is cooked.

Drain the seafood and mix with the dressing. Taste for seasoning and add salt and pepper as necessary.

At this point you could chill the mixture for up to a day in the fridge. Alternatively serve it room temperature or slightly warm, garnished with parsley.