Preheat oven to 350F degrees. Put all ingredients in large, ovenproof casserole dish. Stir to blend. Place the pan over medium-low heat and bring to boil, stirring regularly. Lower the heat and cook for 5 minutes more, continuing to stir.
Slide casserole into oven and cook, until pumpkin butter has thickened and there is no liquid around sides of pan (1 1/2 to 2 hours). Cool pumpkin butter, then cover and chill. Pack airtight; keep in refrigerator for up to one week.