Notch brewing made a session coffee milk stout that was unreal. 10 months later I'm still talking about it they brewed it for the craft beer fest in Boston.
Well, I'm a noob too so bare with me. The process for them is the same but with a Partial Mash you are actually using base grains to convert starches to sugars just like an All Grain method but are using a smaller bill of gains and using less extract to makeup the rest of the wort.
These ingredients can come in handy for a large variety of purposes. Raw ingredients must go through a cereal mash before being used in brewing. Your regular mash must then contain enough enzymes to convert the starches, because these ingredients contain no enzymes of their own.