Globally keyed cache fragments across all controllers

In the documentation for fragment caching
(http://guides.rubyonrails.org/caching_with_rails.html#fragment-caching),
this is stated:

  If you don’t want the cache block to bind to the action that called
it, You can also use globally keyed fragments by calling the cache
method with a key, like so:

  <% cache('all_available_products') do %>
    All available products:
  <% end %>

  This fragment is then available to all actions in the
ProductsController [...]

Is it possible to add a globally keyed cache fragment that is available
in _all_ controllers, not just ProductsController as in the example
above? I plan on having a list of the top 10 items of one of my models,
in my layout, so it'd be ideal to have that cached globally.