
Add water to a large pot over medium-high heat and bring to a boil. Add chopped potatoes and carrots and cook until tender, about 10 minutes.
In the meantime, add the vegan butter or oil to a skillet over medium-high heat. Once melted, add the diced onion, bell pepper and garlic. Cook until veggies are soften and garlic is fragrant, about 3 minutes. Set aside until ready for use.
Drain water from potatoes and carrots. Transfer potatoes and carrots to a food processor along with the cooked onion, pepper and garlic. Add the remaining ingredients, besides the cauliflower and optional breadcrumbs, and process until smooth and creamy.
Lightly oil a square glass baking dish. Add the chopped cauliflower to the bottom of the dish, forming an even layer. Then, pour the sauce over the cauliflower and sprinkle optional breadcrumbs on top. Season the top with salt and pepper.
Bake at 350 degrees F for 30-40 minutes, or until cauliflower is tender. Mine gets done at 30 minutes, but I like baking it for an extra 10 to get the cauliflower super tender.
Serve warm and enjoy!