Like Water for Chocolate is a great novel, that contains love, fight, personal transformation of main characters and shocking traditions. There is so much you can find to write about in your essay on the novel.
I can suggest you several ideas that are perfect for elaborating in your piece.
#1. Illness in Like Water for Chocolate: what does this metaphor stand for?
#2. Love in LIke Water for Chocolate: its role and outcomes. Or you can analyze different forms of love depicted in the novel. A love between a man and a woman. Love for food and cooking. Love to the family. There is so much to talk about!
#3. Feminist novel Like Water for Chocolate. One of the best topics in this novel. But, one of the most popular, too. It would be quite a challenge to say something, that wasn’t already said here.
Also, there is always an easy way. You can analyze the plot itself, ponder about the role of food in the novel or investigate the structure of the novel.