Caramel Popcorn (Mom’s)

24 cups popped corn (1 heaping cup unpopped)
¾ cup brown sugar
¾ cup sugar
½ cup corn syrup
¼ cup water
1/8 tsp. cream of tartar
3 Tbsp. butter
½ tsp. soda
1 cup nuts, optional

In 3-quart saucepan cook sugars, corn syrup, water, cream of tartar and butter to 234°F or softball stage. Let boiling subside. Add soda and nuts. Pour over popped corn and toss.