1. Make crust: Preheat oven to 350°F. Combine wafers and sugar in a food processor and pulse until finely ground. Add butter and pulse until crumbly, about 10 seconds. Press mixture evenly over bottom and slightly up sides of a 10-inch springform pan (mixture will be dry). Bake until firm and set, 8 to 10 minutes. Let cool completely in pan on a wire rack.
2. Make filling: Place malted milk balls in a large ziplock bag. Seal bag and crush candies with a rolling pin. Set aside 1/2 cup of crushed candies for garnish. In a large bowl, stir ice cream, malted milk powder and remaining crushed candies. Spread evenly over bottom of cooled crust, smoothing top. Freeze until firm, at least 1 hour.
3. Make glaze: Place chocolate in a small heatproof bowl. Bring cream to a boil in a small pan over medium-high heat. Pour over chocolate and let sit for 2 minutes. Whisk until completely smooth. Working quickly, pour glaze over pie and spread evenly. Sprinkle with reserved crushed candies. Freeze until firm, at least 3 hours or overnight.
4. Remove cake from freezer 10 minutes before serving and let sit at room temperature. Just before serving, run a sharp knife around pan edges, loosen pan sides and unmold to a plate. Use a sharp knife to cut cake into wedges.