How to Make It
Preheat oven to 350°F. Grease a metal 9- x- 13 inch baking dish with cooking spray.
In a large mixing bowl, whisk together half-and-half, sugar, eggs, nutmeg, cinnamon, ginger, and vanilla until well combined. Add pumpkin and whisk to combine. Once fully incorporated, whisk in 1/4 cup of the melted butter. Evenly spread mixture in prepared baking dish.
Sprinkle cake mix evenly over pumpkin mixture. Drizzle remaining 3/4 cup melted butter on top of cake mix, and use a spoon to gently spread the butter around, encouraging the butter to soak into the cake mix. Bake until top is browned and fully cooked through, about 1 hour.
Allow to cool to room temperature for filling to set completely. Serve with whipped cream and more nutmeg, if desired. Serve warm or chilled.