1. Preheat oven to 325 degrees F. In 1 quart heavy saucepan, stir together butter, whipping cream, and brown sugar. Cook over low heat, stirring occasionally, just until butter is melted. Pour into 2 (8 or 9 inch) round cake pans; sprinkle evenly with 3/4 cup pecans.
2. In large bowl, beat cake mix, pumpkin, milk, oil, eggs, and 1 teaspoon of the pumpkin pie spice with electric mixer on low speed until well moistened. Beat 2 minutes on medium speed. Carefully spoon batter over pecan mixture in each pan.
3. Bake 43-45 minutes or until cake springs back when touched lightly in center. Cool 5 minutes; remove from pans to cooling racks. Cool completely, for about 1 hour.
4. Stir remaining 1/2 teaspoon pumpkin pie spice into frosting. To assemble cake, place 1 layer, praline side up, onto serving plate. Spread with half of the frosting. Top with second layer, praline side up; spread with remaining frosting to the edge of layer. Drizzle with caramel topping and additional pecans.