Rendering resolved promise value in Ember handlebars template

Is there a good way to render the result of a promise in a handlebars template?

For example, I have the following model:

App.TopicItem = DS.Model.extend({
  topic: DS.belongsTo('topic'),
  paddedPosition: function() {
    return this.get('topic.course.lessons').
      then(function(lessons) {
        return lessons.indexOf(topicItem);
      }).
      then(function(index){
        var position  = index;

        if (position < 0) { 
          return;
        }

        position = position + 1;

        return (position < 10 ? $.rjust(position, 2, '0') : position.toString());
      });
  }.property('topic.course.lessons')
});

And I would like to render the value of the position in the handlebars template like this:

{{topicItem.paddedPosition}}

Is there a good way to accomplish this?