Yes Matthew, adding more layers. Some people are very scientific about these things but I am not. But the way I look at it is that the plants we are growing are constantly taking something from the soil so we need to constantly put something back.
Pioneers in sustainablegardening methods such as Ruth Stout and Bill Mollison recommend just taking your compostable items and tucking them in here and there under the top layer of mulch; this is done all the time (as it comes out of the kitchen).
Mollison believes that if you have an established worm colony in your garden they will quickly eat the refuse, turning it into worm manure and you will instead have worm manure spread all over your garden. Seasonally you would add leaves or grass clippings or whatever happens to be available. Kind of like what happens in nature - in the forest.
Edited to add: I don't think you're going to have grass clippings in a forest but I like to use a lot of them anyway