1 to 2 teaspoons...
self control is a must
I work for a major grocery chain dairy. We make Ice Cream 6 days a week 50 weeks a year.... it gets old quickly.
PS: We make frozen yogurt too... If you buy either buy the premium brands... most ice cream only has the very minimum butterfat allowed by law.
Premium brands (includes store brands) have 16% - 25%