I start by mixing the cake mix, eggs, oil, and water according to the package directions, then pour the batter into a greased 9x13-inch pan. I bake it at 350°F for about 25 to 30 minutes, until a toothpick comes out clean. Once it's done, I let it cool completely on a wire rack before touching it.
Once the cake is fully cooled, I cut it into 1-inch cubes. I know it's tempting to rush this step while the cake is still warm, but warm cake crumbles and makes your trifle layers look messy instead of clean and defined.
In a large bowl, I whisk the cold milk, pumpkin puree, pudding mix, and pumpkin pie spice together for about two minutes, until it thickens slightly. Then I gently fold in half of the whipped topping until the mixture turns light and fluffy, not stiff.
I start with a layer of cake cubes at the bottom of my trifle bowl, then spoon on a generous layer of the pumpkin filling, followed by a sprinkle of pecans and toffee bits. I repeat this two to three times depending on the size of my bowl, finishing with a pretty layer of whipped topping on top.
I always cover the trifle and refrigerate it for at least two hours before serving. This resting time lets the cake soak up some of that creamy filling and makes every bite taste like it was meant to go together.