Heat butter in a 9-inch skillet. Cook the onions and peppers until soft and onions are a little brown. Cool to room temperature. Butter a 2 quart baking dish (not too deep).
When cool transfer these to a mixing bowl and add cornstarch, cream, egg yolks and mustard. Whisk well to blend.
Fold the corn and turkey into the egg mixture. Season with salt and pepper. Beat the egg whites until they hold stiff peaks but are not dry and fold them into the egg yolk mixture. Transfer to the buttered baking dish and bake for 35 to 40 minutes or until brown and puffy.
Serve with a side dish of sliced ripe tomatoes and vinaigrette.