1Heat oven to 350°F (325°F for dark or nonstick pan.) Spray 13x9-pan with baking spray with flour.
2In large bowl, stir together cake mix and 3/4 cup malted milk powder. Beat in water, oil and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Pour batter into pan.
3Bake 38 to 43 minutes or until toothpick inserted in center comes out clean. Cool completely, about 1 hour.
4In medium bowl, beat cream, 3/4 cup malted milk powder and the vanilla on low speed until blended, then on high speed until stiff peaks form. Spread over cake. Place malted milk balls in small resealable freezer plastic bag; seal bag and crush with rolling pin or meat mallet. Just before serving, top with chopped malted milk balls. Store covered in refrigerator.