In large bowl, combine cake mix, water, oil, and eggs at low speed until moistened; beat 2 minutes at highest speed. Carefully spoon batter over pecan mixture.

Bake at 325 degrees 35 to 45 minutes or until cake springs back when lightly touched in center. Cool 5 minutes. Remove from pans. Cool completely.

Topping: In small bowl, beat whipping cream until soft peaks form. Blend in powdered sugar and vanilla; beat until stiff peaks form.

To assemble cake: Place one layer on serving plate, praline side up. Spread with half of whipping cream. Top with second layer, pralines side up; spread top with remaining whipping cream. Garnish with whole pecans chocolate curls. Store in refrigerator.