Pour the chili into the bottom of a 9" cake pan, making an effort to leave most of the liquid behind (see note).
Spread the cauliflower mashed potatoes over the top of the chili, and bake for 30 minutes. Let the chili pie sit for 10-15 minutes before serving. Sprinkle on the green onions just before serving.
Notes
The prep time is the time it takes to make the Cauliflower Mashed Potatoes.
About the chili: Use leftover chili, your favorite homemade chili, or (I'll never tell!) 3 15-ounce cans of premade vegan chili. You'll have the best results if your chili isn't too liquidy, so drain off any excess liquid as you measure by scooping the chili with a 1 cup measuring spoon and tilting it against the side of the bowl before you transfer to the cake pan. Most of the liquid will run off, but the beans and other goods will stay in the spoon.