1Heat oven to 325. In small heavy saucepan, combine butter, 1/4 cup heavy cream and brown sugar. Cook over low heat just untill butter is melted, stirring occasionally. Pour into two 9 or 8-inch round cake pans; sprinkle evenly with chopped pecans.
2In large bowl, combine cake mix, water, oil and eggs at low speed until moistened; beat 2 minutes at high speed. Carefully spoon batter over pecan mixture.
3Bake 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 completely.
Whip heavy cream until soft peaks form. Blend in powdered sugar and vanilla.
5To 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.