How to Make It
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 bottom of prepared baking dish. Whisk together sweet potato puree, cream cheese, light brown sugar, salt, and remaining egg in a large bowl until smooth. Pour sweet potato mixture over dough mixture. Bake in preheated oven until just set, about 30 minutes.
Meanwhile, stir together graham cracker crumbs, oats, 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.