Thaw seafood in cold water for 10–15 minutes and pat dry with paper towels.
Melt butter and olive oil in a large pot over medium heat.
Whisk in flour to form a roux and cook until bubbly.
Slowly pour in milk and seafood broth, stirring constantly.
Add diced potatoes and onions. Simmer for 15 minutes or until tender.
Stir in thawed seafood and cook uncovered for 5-7 minutes until shrimp turns pink.
Season with lemon juice and adjust salt and pepper to taste.
Garnish with chopped parsley and serve with crusty bread.