Add approximately two inches of water to the bottom of a large pot with cover. Add diced sweet potatoes to the pot, then place the cauliflower florets on top of the sweet potatoes.  Over high heat, bring water to a boil.  Reduce to a fast simmer and cover, then cook for 10 minutes or until vegetables are tender and soft when pierced with a fork.

While sweet potatoes and cauliflower simmer, melt butter in a small skillet.  Add diced onion, and sauté over medium heat until onions are soft and translucent, about 3 to 4 minutes. Remove from heat and set aside.

Once sweet potatoes and cauliflower florets are cooked through, pour into a colander.  Place vegetables back in the pot and mash with a potato masher, mixing the sweet potatoes and cauliflower together.

At this point you have a choice – leave the sweet potatoes and cauliflower as a chunkier mash, or you can puree the mixture in a food processor like we did for a smoother texture.  If leaving as a chunkier mash, stir in the butter-onion mixture and the garlic powder, white pepper and salt, mixing to combine.

If you want a smoother mixture, add the mashed sweet potatoes and cauliflower to a food processor along with the butter and onion mixture and seasonings.  Process until smooth.

Serve immediately.