Created for other purposes but this noise pattern is quite versatile. In the image below it is used for the chocolate sprinkles but bacteria and some forms of dust is what it originally was intended for:
As always, example code and node setups are available on my blog:
I know the crust in the image above looks completely fake but that was not what I was focussing on, however, I am still trying the improve the display of the sprinkles themselves because although they are displaced, they still look a bit flat. I think I can improve that by reducing the gloss and darkening the difuse close to the edge of the sprinkles as these edges are lower and receive less light, kinda like AO. But I am interested to hear other suggestions.