Crust: Heat oven to 325°. Combine cake mix and butter in large bowl, mixing at low speed until crumbly. Set aside 1 cup of mixture for topping. Press remaining mixture in bottom and 1 1/2 inches up sides of ungreased 10 inch springform pan.
Filling: In a mixing bowl, beat cream cheese and 1 cup brown sugar until smooth. Add the pumpkin, cornstarch, cinnamon, and nutmeg; mix well. Gradually beat in milk, eggs, and vanilla just until blended. Pour into crust. Sprinkle the topping evenly over filling. Place pan on a baking sheet. Bake at 325° for 70-80 minutes or until center is almost set and topping is golden brown. Remove from oven and drizzle caramel topping over top. Bake for 8-10 minutes more to set topping. Cool 30 minutes. Run knife around sides of pan to loosen. Cool completely. Remove sides of pan and refrigerate 4-5 hours or overnight. Store in refrigerator.
Topping: In small bowl combine reserved crumb mixture, 1/2 cup brown sugar, and pecans; blend well. Drizzle with additional caramel when serving.