Preheat oven to 350°. Halve the peppers lengthwise and remove seeds and membrane.
Blanch for 5 minutes in boiling water, drain and set aside.
Melt 3 tablespoon butter and sauté the shallot until soft. Sprinkle with flour and cook until bubbly.
Remove from the heat and add the cream cheese. Cook and stir over low heat until all incorporated. Add lemon juice, mustard parsley.
In a small frying pan add 1 tablespoon of butter and sauté the prawns until light pink. Add 1 teaspoon lemon juice and cook over medium heat for another minute.
Add the prawns to the cream cheese mixture and mix well. Season with salt and pepper.
Spoon into pepper shells and sprinkle with cheese.
Bake for 30 minutes or until heated through and cheese is bubbly.