Preheat oven to 400 degrees F (204 C) and lightly grease (or line with parchment paper) 2 large, rimmed baking sheets (use fewer or more baking sheets, as needed, if altering batch size). Also lightly grease a small baking dish (8x8 inch is ideal // size as original recipe is written // adjust if altering batch size)).
Add halved sweet potatoes to one baking sheet, and the cubed butternut squash to another. Drizzle each with half of the avocado or melted coconut oil (1 Tbsp as original recipe is written // adjust if altering batch size).
Sprinkle with a pinch of salt and pepper. Rub sweet potatoes together to distribute the oil, and toss the butternut squash as well.
Roast butternut squash for 15 minutes, then remove from oven and test doneness. It should be very fork tender and easily mashed. Once it's done, remove from oven and set aside.
Depending on the size of your sweet potatoes, they should take anywhere from 20-35 minutes total. Remove from oven when very soft to the touch. Then reduce oven heat to 350 degrees F (176 C).
Heat a large skillet over medium heat. Add chopped pecans and toast for 5 minutes, stirring frequently. If smoking or browning too quickly, turn heat to medium-low or low.
At the 5-minute mark, add coconut oil, coconut sugar, maple syrup, cinnamon, and salt. Stir to coat and cook for another 1-2 minutes. Remove from heat and set aside.
Peel sweet potatoes and add to a large mixing bowl with butternut squash. Use a fork, potato masher, or whisk to thoroughly mash.
Add another pinch salt + pepper, ground cinnamon, maple syrup, and vegan butter. Mash once more to combine, then taste and adjust seasonings as needed.
Transfer mashed squash and potatoes to prepared baking dish and top with toasted pecans. Add vegan butter, cubed, to add additional moisture and flavor (optional).
Bake for 10-15 minutes or until completely warmed through and fragrant. Let cool briefly and then serve.
Leftovers store well in the refrigerator for 2-3 days, though best when fresh. Reheat in a 350-degree F (176 C) oven or in the microwave.