I came back from Atlanta with this recipe for Oreo Balls, where these extraordinatry cookies were served at my nephew's bar mitzvah. These no-bake (but messy-to-make) cookies, which can be prepared in advance by children, are so delicious that we've designed our Purim baskets around them. This Purim's Mishloach Manot will be black and white. And as they are dairy, we traditionally make them for Shavuot.
NOTE: The balls can be prepared several weeks before an event and stored in the freezer.