Step 1

Preheat oven to 350°F. Whisk together pumpkin, evaporated milk, sugar, eggs, and 1 teaspoon of the cinnamon in a medium bowl to combine. Pour mixture into a lightly greased 13- x 9-inch baking dish lined with parchment paper.

Step 2

Sprinkle 1 1/2 cups of the cake mix evenly over top of pumpkin mixture; sprinkle with chopped pecans. Sprinkle remaining cake mix over nuts. (Do not stir!)

Step 3

Drizzle butter evenly over cake mix. Bake in preheated oven until golden brown and set, about 50 minutes.

Step 4

Cool to room temperature on a wire rack, about 1 hour. Invert pan onto a cutting board, and refrigerate at least 1 hour until well chilled. Trim edges, and cut into 24 squares.

Step 5

Stir remaining 1/4 teaspoon cinnamon into whipped cream. Add mixture to a large ziplock plastic bag, and snip a small corner of the bag. Pipe whipped cream on top of each square. Garnish with 1 pecan half piece.