Sub menus - How to?

I have spent about loo long failing to get menus to work. I’m trying to get something like the hugo documentation site. I have read through several posts here about menus and still can’t get it to work.

I am expecting to put the top level menu item in the config.toml, give it an identifier and then in the front matter of each page that represents a sub-menu item link back to the parent.

Using

Hugo Static Site Generator v0.18.1 BuildDate: 2017-01-06T21:04:35Z

/config.toml

[[menu.main]]
  identifier="unique1"
  name="Unique 1"
  weight=-170

/content/unique1/aTopic.md

+++
draft=true
date="2017-01-09T07:00:54Z"
title="Unique 1"
[menu]
[menu.main]
parent="unique1"
+++
Really interesting content

I’m running with hugo serve -t blackburn -w -D

The first menu item “Unique 1” appears and the html looks ok, there are no javascript errors. rendered HTML;

<li class="pure-menu-item pure-menu-has-children">
  <a class="pure-menu-link" href="#">Unique 1</a>
  <ul class="pure-menu-children">
    <li class="pure-menu-item">
      <a href="/unique1/aTopic/">A Topic</a>
    </li>
  </ul>
</li>

Any hints as to my error would be appreciated.

Update: I’m using the Blackburn theme. I think that’s where the issue lies

Can you link to the repo?

I put the sample which reproduces it here.

Thanks for looking

Yeah, I think it’s the theme too. Hugo is creating the menu with children correctly for me. The author’s comments in his side-menu.css says that he custom made the open/close button, so it is likely either the css or the js.