Preheat oven to 325 degrees F. Coat a 9-inch deep-dish pie pan with cooking spray.

To prepare crust: Combine chocolate wafers and dates in a food processor; process until finely chopped. Add water and oil and process until moistened. Press into the bottom and sides of the prepared pan.

Bake until crisp, about 10 minutes. Cool completely on a wire rack.

To prepare filling & garnish: Combine coffee and water in a small bowl. Sprinkle gelatin on top and set aside to soften.

Whisk egg, milk, 3 tablespoons brown sugar and cocoa in a small saucepan until smooth. Cook over low heat, whisking constantly, until thickened and an instant-read thermometer registers 160 degrees F, 5 to 7 minutes. Do not let the mixture come to a simmer. Remove from the heat. Add the reserved gelatin mixture; stir until dissolved. Add chocolate and vanilla, stirring until melted. Set aside to cool to room temperature, about 30 minutes.

Beat reconstituted egg whites and cream of tartar in a large bowl with an electric mixer on low speed until frothy. Increase speed to high and beat until soft peaks form. Gradually add the remaining 5 tablespoons brown sugar, beating until the meringue is smooth and glossy.

Whisk one-fourth of the meringue into the cooled chocolate mixture until smooth. Scrape the chocolate mixture into the remaining meringue and fold in with a whisk. Spoon the filling into the crust and chill, uncovered, until set, about 3 hours.

Tip: Many commercial cookies and wafers contain partially hydrogenated oil, a source of trans-fatty acids. Look for brands made without these oils, such as Newman's Own Organics and Mi-Del, which fortunately are every bit as tasty. Find them in the natural-foods section of large supermarkets.

Ingredient Note: Dried egg whites are pasteurized-a wise choice when making meringue toppings that may not reach 160 degrees F (the temperature at which eggs are considered "safe"). You'll find them in the baking or natural-foods section of most supermarkets. Reconstitute according to package directions.

MAKE AHEAD TIP: Cover and refrigerate for up to 2 days. | Equipment: 9-inch deep-dish pie pan