Heat oven to 325 degrees. In a small saucepan, stir together butter, whipping cream and brown sugar. Cook over low heat, stirring occasionally, just until butter is melted. Pour into two ungreased 9 or 8 inch round cake pans; sprinkle evenly and with 1 cup of pecans.
In a large bowl beat cake mix, pumpkin, water, oil, eggs and 1 teaspoon of the pumpkin pie spice with electric mixer on low speed until moistened, then on medium speed for 2 minutes, scraping bowl occasionally. Carefully and slowly spoon batter over pecan mixture in each pan.
Bake 40-47 minutes or until cake springs back when touched lightly in center. Cool only 5 minutes; remove from pans to cooling rack. (It is important to not let the cakes cool any longer than 5 minutes or the praline mixture will harden and will be difficult to remove from the pan).
After cake removal let cool for about an hour.
Stir remaining 1/2 teaspoon pumpkin pie spice into frosting. To assemble cake, place 1 layer, praline side up on serving plate. Spread with half of frosting only on the top of the cake, not sides of cake. Top with second layer, praline side up and spread remaining frosting, again, on the top of the cake, not the sides. Drizzle with the caramel topping and additional pecans.
If not serving for sometime after baking you can store it loosely covered in the refrigerator.