Get a set of related records from multiple related records laravel?

I have users that have multiple restaurants, then each restaurant has comments.

So when a user logs in, I would like to show a list of all the comments from restaurants related to the user.

I am using laravel 5.1

What I have so far is:

$restaurants = $user->restaurants;
        $comments = null;
        foreach ($restaurants as $restaurant) {
            if (!$comments){
              $comments = $restaurants->comments();
            } else{
              $comments = $comments->merge($restaurant->comments());
            }
        }

        $rows = $comments->paginate(15);
        $count = $comments->count();

I get a BadMethodCallException, I think I am not doing this the laravel way.

via Chebli Mohamed