Preheat oven to 350°F (175°C). Combine crushed chocolate graham crackers, sugar, and melted butter in a food processor until evenly mixed. Press into the bottom and slightly up the sides of a 10-inch (25 cm) springform pan. Bake for 8 to 10 minutes, or until set. Cool completely.
1⅔ cups (170 g) crushed chocolate graham crackers, ¼ cup (50 g) granulated sugar, 4 tbsps (57 g) unsalted butter
Place the Whoppers in a zip-top bag and crush with a rolling pin or mallet. Reserve ½ cup of the crushed candy for the topping.
1 carton (12 oz / 340 g) Whoppers malted milk balls
In a large bowl, stir together the softened vanilla ice cream, malted milk powder, and the remaining crushed Whoppers until evenly combined.
2 quarts (1.9 L) vanilla ice cream, ½ cup (65 g) malted milk powder
Spread the ice cream mixture into the cooled crust and smooth the top. Freeze for 1 hour.
To make the topping, heat the heavy cream in a small saucepan until it just reaches a boil. Pour over the chocolate chips and let stand for 1 minute. Whisk until smooth.
½ cup (120 ml) heavy cream, 7 oz (198 g) semi-sweet chocolate chips
Pour the chocolate mixture over the partially frozen ice cream cake and spread evenly. Sprinkle with the reserved crushed Whoppers.
Freeze until firm, at least 6 hours or overnight.
Remove the cake from the freezer and let stand for 5 minutes. Run a knife around the inside edge of the pan and release the springform ring. Transfer to a serving plate and slice with a sharp knife.