Preheat oven to 350°.
To prepare crust, combine crushed wafers, 1 tablespoon sugar, and egg white in a bowl; toss with a fork until moist. Press into bottom and sides of a 9-inch springform pan coated with cooking spray. Bake 15 minutes; cool on a wire rack.
Spoon 3 cups ice cream into cooled crust, spreading evenly. Cover with plastic wrap; freeze until firm. Repeat process with sherbet; freeze again until firm. Spread remaining 3 cups ice cream over sherbet; sprinkle with minichips. Freeze overnight or until firm.
To prepare sauce, combine water, 1 cup sugar, and corn syrup in a small saucepan over medium heat. Bring to a boil; reduce to low and simmer until slightly thick (about 15 minutes). Remove from heat; stir in grated chocolate and cocoa; whisk until smooth. Stir in evaporated milk and vanilla.
Make sure torte is thoroughly frozen before slicing. Spoon about 2 1/2 tablespoons sauce over each slice of torte. Top with raspberries and mint sprigs, if desired.