Heat oven to 350°F (325°F for dark or nonstick pans). Grease two 8- or 9-inch round cake pans, or spray with baking spray with flour.
Make and bake cake mix as directed on box for two 8-inch or 9-inch rounds. Cool 10 minutes. Run knife around sides of pans to loosen cakes; remove from pans to cooling rack. Cool completely, about 1 hour.
In 1-quart saucepan, heat caramels, butter and whipping cream over medium heat 6 to 8 minutes, stirring frequently, until caramels are melted and mixture is smooth. (Or place caramels, butter and whipping cream in 4-cup glass measuring cup; microwave uncovered on High 1 to 3 minutes, stirring once or twice.) Stir pecans into melted caramel. Cool 30 to 45 minutes or until firm enough to spread without running over edge of cake.
Place 1 cake layer on plate, round side down. Spread with 1 cup of the pecan filling. Top with second layer, round side up. Spread remaining pecan filling into 4- to 5-inch circle on top of cake. Spread chocolate frosting on rest of top and side of cake. Store loosely covered.