"Bring your favorite ___________ to share with the group." Fill in the blank with whatever you want, casserole, dessert, appetizer, finger food, soup, salad, etc. You can then customize it to the event or theme and the person making sure several folks get a particular category. That way you won't get stuck with all the same thing. We often held potlucks in our home for our church Bible study group. We would have soup nights, Mexican night where everyone brought a component of tacos (someone would do beef filling, someone chicken, someone would do shells, another would do sour cream and cheese, another veggies etc.) For the first meeting I would do signature dishes and you can then use that as a "getting to know you" starting point.
I could give up chocolate but I'm no quitter!