In a large pot sauté the scallops in the butter then set aside.
In the same pot sauté the celery, red pepper and onion until tender. Sprinkle in the flour and stir until blended. Gradually stir in the milk, cream, stock and seasonings, and bring to the boil. Reduce heat and let simmer for 2 minutes or until thickened.
Add the prawns and return the scallops to the pot warm through and serve.
I used pre cooked shop bought red peppers in a jar. You can use a pepper you've roasted yourself, as well.