Spread the butter evenly around the bottom and sides of one large, 2-quart souffle dish. Pour 3 tablespoons of sugar into the mold, and rotate until all sides are covered. Refrigerate.
Dilute the cornstarch in the cold milk. In a heavy-bottomed 2-quart sauce pan, bring the milk, the remaining sugar, and the vanilla to a boil. Beat together the egg yolks in a medium bowl. Add a small amount of the hot milk mixture to the beaten eggs. Then add the egg mixture back into the pan with the hot milk. Cook, stirring for 3 to 5 minutes, or until the mixture thickens substantially. Remove the pan from the heat, stir in the peanut butter, and place in a bowl to cool.
Preheat the oven to 400 degrees.
Prepare the strawberry sauce: bring the cup of water and the sugar to a boil in a sauce pot over high heat. Add the strawberries, and simmer for fifteen minutes. Remove from the heat and allow to cool slightly. Puree the entire contents of the pot in the blender. Pour the sauce into a pitcher, and keep warm.
When the peanut mixture is cool, whip the egg whites, 1/4-cup sugar, and the salt until silky, stiff, and not dry. In a large bowl, using a rubber spatula, mix 1/3 of the whites into the peanut mixture to lighten up. Then fold the remaining egg whites in very gently, turning the bowl in a circular motion, until the batter is uniformly incorporated and light. Immediately pour into the souffle mold, and bake for ten minutes. The souffle should move only slightly when shaken gently. Dust with confectioners' sugar and serve at once, with the strawberry sauce on the side.