The vegetable mash is rich in vitamin A and potassium, thanks to butternut squash.
Heat oil in a large pot over medium-high heat. Add squashes and salt. Cover, and cook, stirring occasionally, until partially tender, about 8 minutes (reduce heat if squash begins to brown). Add 1 cup water, cover, and simmer over medium-high heat until completely tender and water has mostly evaporated, about 15 minutes. Mash with a potato masher. Season with pepper.