Cleaver uses the marked library for markdown processing. The conversion happens in renderSlide:

https://github.com/jdan/cleaver/blob/master/lib/index.js#L27...

  /**
   * Renders a slide.
   *
   * @param {string} content Markdown content to be rendered as a slide
   * @return {string} The formatted slide
   */
  Cleaver.prototype.renderSlide = function (content) {
    return marked(content);
  };