Dice the butternut squash, carrot, potato, and onion into equal-sized pieces.
Bring a saucepan of water, about 1/2 gallon (2 liters), to a boil. Add the chopped vegetables and the concentrated stock. Reduce to a simmer and cook until the vegetables are tender.
When the vegetables are cooked mash them with a potato masher. Add the herb rub to taste. Serve hot.