Menu - Get child entries

I have a menu and want to build a "mega menu" and i need an individual layout for the child lists/items.

So if i dump my menu i have a children array with all child pages. Now i want to loop through this childs with

<ul>
  {{ foreach:children }}
    <a href="{{ url }}">{{ title }}</a>
  {{ /foreach:children }}
</ul>

But i don't get the children values - With {{ title }} i am getting the title from the parent menu item, not from the child. ( title etc. is of course available inside the children array )

I think i am using maybe the foreach from Statamic wrong?