Vulcan/packages/custom/lib/client/templates/custom_post_title.js

// important: the helper must be defined on the *old* "post_title" template

Template.post_title.helpers({
  randomEmoji: function () {
    return _.sample(["😀", "😰", "👮", " 🌸", "🐮", "⛅️", "🍟", "🍌", "🎃", "⚽️", "🎵"]);
  }
});