We did something similar on Philosophy, where we designate one philosopher each week, and each person who asks a question relating to that philosopher is eligible to win a prize. It's gotten a positive response so far, and we could easily adapt the model for this site - that is, designate a cooking topic each week, and everyone who asks a question about it that week is entered into a drawing to win prizes.
Some example topics are bread baking, vegan cooking, recipe scaling, breakfast foods, etc. A great way to start would be to think about topics that are popular during the holidays and begin with those.
What do you think? If you have suggestions for weekly topics, please leave them here as well!