In a medium saucepan, heat the milk and vanilla bean to a boil over medium heat. Immediately turn off the heat and set aside to infuse for 10 minutes. In a bowl, whisk the egg yolks and granulated sugar until light and fluffy. Add the cornstarch and whisk vigorously until no lumps remain. Whisk in 1/4 cup of the hot milk mixture until incorporated. Whisk in the remaining hot milk mixture, reserving the empty saucepan.
Pour the mixture through a strainer back into the saucepan. Cook over medium-high heat, whisking constantly, until thickened and slowly boiling. Remove from the heat and stir in the butter. Pour into individual dessert dishes and chill. Chill at least 2 hours or until ready to serve. (The custard can be made up to 24 hours in advance. Cover with plastic wrap if you are keeping it longer than that.)
Raspberry Mash: Place 1/4 of a pint of raspberries in a bowl with the sugar and mash it with the back of a fork. Toss in the remaining 1/4-pint of raspberries and gently toss to coat.
Whip the cream with the sugar and serve on the custard and mash.