How to Make It
Preheat oven to 300°.
To prepare crumble, place wafers in a food processor; pulse 15 times or until fine crumbs form. Add 2 tablespoons butter, and pulse 4 times or until mixture resembles coarse meal. Add vanilla extract and egg white, and pulse just until moist. Spread crumb mixture onto a baking sheet coated with cooking spray, pressing gently. Bake at 300° for 27 minutes or until golden, and let stand 10 minutes. Crumble and set aside.
To prepare custard, heat the milk and vanilla bean over medium-high heat in a large, heavy saucepan to 180° or until tiny bubbles form around edge (do not boil), stirring frequently. Remove from heat, and let stand 30 minutes. Remove vanilla bean from pan. Scrape the seeds from vanilla bean, and add seeds to milk mixture. Discard bean. Add sugar, cornstarch, and salt to milk mixture, stirring with a whisk. Bring to a boil over medium-high heat, stirring frequently. Cook 1 minute, stirring constantly. Remove from heat.
Place egg yolks in a medium bowl, and stir with a whisk. Gradually add hot milk mixture to egg yolks, stirring constantly with a whisk. Return milk mixture to pan. Bring to a boil, and cook 1 minute, stirring constantly. Remove from heat; add 1 teaspoon butter, stirring until butter melts. Place pan in a large ice-filled bowl for 30 minutes or until the mixture comes to room temperature, stirring occasionally. Cover and chill 8 hours or until set. Combine the berries. Place 1/4 cup crumble in each of 8 (8-ounce) custard cups, and top each serving with 1/4 cup custard. Spoon 2 tablespoons berry mixture over each serving.