Heat oven to 325°F. In small heavy saucepan, combine butter, 1/4 cup whipping cream and brown sugar. Cook over low heat just until butter is melted, stirring occasionally. Pour into two 9 or 8-inch round cake pans; sprinkle evenly with chopped pecans.
In large bowl, combine cake mix, water, oil and eggs; beat at low speed until moistened. Beat 2 minutes at medium speed. Carefully spoon batter over pecan mixture.
Bake at 325°F. for 35 to 45 minutes or until cake springs back when touched lightly in center. Cool 5 minutes; remove from pans. Cool 1 hour or until completely cooled.
In small bowl, beat 1 3/4 cups whipping cream until soft peaks form. Add powdered sugar and vanilla; beat until stiff peaks form.
To assemble cake, place 1 layer on serving plate, praline side up. Spread with half of whipped cream. Top with second layer, praline side up; spread top with remaining whipped cream. Garnish with whole pecans and chocolate curls. Store in refrigerator.