Preheat oven to 350 and grease and flour a 13x9 baking pan.
Remove 1 cup of the cake mix; reserve. In small bowl, lightly beat 1 egg. In large bowl, stir together remaining cake mix, melted butter and the beaten egg.
Press into prepared pan.
In large bowl, lightly beat remaining 3 eggs, Stir in the pumpkin, 1/2 cup of the sugar, brown sugar, evaporated milk and cinnamon. Pour over cake mixture in pain. To the 1 cup reserved cake mix, add remaining 1/2 cup sugar, walnuts and softened butter; mix until crumbly. Sprinkle over pumpkin mixture.