Preheat oven to 350 degrees.
Prepare a 9x13 baking dish by spraying with nonstick cooking spray.
Beat the pumpkin, brown sugar, molasses and softened non-dairy margarine in the bowl of an electric mixer on medium speed until well combined.
In a separate bowl, combine the flour, baking powder, baking soda, 1/2 package of the pumpkin pie pudding, and additional pumpkin pie spice, if desired. Whisk well to incorporate.
Add the flour mixture to the pumpkin mixture in small increments and alternating with the boiling water. Beat on low speed after each addition.
Spread evenly into baking dish and bake for approximately 35-45 minutes or until a toothpick inserted comes clean.
Cool completely on a wire rack.
Meanwhile, to prepare the vanilla pudding, add 1 C of VERY COLD non-dairy milk to the pudding in the bowl of an electric mixer. After two minutes, if it is already getting thick, add a bit more milk. After 5 minutes of beating, it should start to look like pudding. Refrigerate for at least 1 hour where it will reach a thicker consistency.
****THE KEY TO ACHIEVING A SUCCESSFUL VEGAN PUDDING IS STRIKING THE CORRECT BALANCE WITH THE LIQUIDS. You can always add, but you can't take away.*****
In a small fry pan, slowly toast the coconut flakes to a golden brown. Set aside.
Once cooled, cut the cake into 1" cubes.
Layer the cubes into the bottom of your trifle dish, then the pudding and repeat.
Top with a bit more pudding and the toasted coconut flakes.
Assemble and serve immediately.