Meanwhile, in 1 1/2-quart saucepan, melt 4 tablespoons butter over medium heat. Add 1/2 cup brown sugar and 1/2 cup chopped pecans; cook 2 to 4 minutes, stirring frequently, until sugar melts and pecans smell toasted. Reduce heat to low; carefully stir in whipping cream and vanilla. Heat to simmering. Cook 1 to 2 minutes, stirring constantly, until thickened. Pour over cooked biscuits.