Prepare & bake the cake according to package directions for two 9-in. round baking pans. Cool for 10 minutes before removing from pans to wire racks to cool completely.
Meanwhile, in a small saucepan, combine the brown sugar, butter &cream. Cook & stir over low heat until sugar is dissolved. Increase the heat to medium; do not stir. Cook for 4-6 minutes or until bubbles form in the center of the mixture & the color is amber brown. Remove from the heat; stir in the pecans. Cool at room temperature for 20 minutes, stirring occasionally.
In a small bowl, whisk pudding mix and milk for 90 seconds. Let stand for 2 minutes. Fold in the whipped topping. Cover and refrigerate until thickened, about 20 minutes.
Place one cake layer on a serving platter; spread with ¾ cup of the pudding mixture. Top with remaining cake layer; spread remaining pudding mixture over top and sides of cake.
If necessary, reheat pecan mixture over low heat to achieve a spreading consistency. Spoon pecan mixture around edge & middle of cake. Store in the refrigerator.