Melt 1 tablespoon of the butter to a heavy-bottomed pot. Add the onions and garlic and cook until tender and golden brown. Then remove from the pot and set aside.
Bring to a boil then simmer covered for about 1 hour, until the meat is tender. Add the butternut squash to the top of the stew, do not stir in. Replace the lid and cook for another 30 minutes.