- Preheat oven to 350°F. Lightly coat a 13- x 9- glass baking dish with cooking spray. Line baking dish with parchment paper, leaving 3 inches of overhang on each side to use as “handles” later. Lightly spray parchment with cooking spray.
- Stir together cake mix, 1/2 cup of the melted butter, and 1 of the eggs in a medium bowl until a firm but smooth dough is formed (it will be cookie dough consistency). Press mixture in an even layer into the bottom of the prepared baking dish.
- Whisk together the pumpkin puree, cream cheese, light brown sugar, salt, and remaining egg in a large bowl until smooth. Pour pumpkin mixture over dough mixture. Bake in preheated oven until just set, about 30 minutes.
- Meanwhile, stir together graham cracker crumbs, oats, spices, pecans, white chocolate chips, and remaining 1/4 cup melted butter in a medium bowl. Sprinkle mixture over baked sweet potato cake. Place back in oven, and bake until nuts and oats are toasted, about 9 minutes. Remove from oven, and let cool to room temperature on a wire rack, about 2 hours. Chill 1 hour, or up to overnight.
- Using parchment “handles”, lift cake out of baking dish and place on cutting board. Cut into 20 squares to serve.