Recently two unreliable narrators, Carl and the Intertubes -- as described by Ando the elder, claimed that premustarding your burgers made for a better burger. In each case the referent was the famous In and Out burger. To resolve the issue we undertook a scientific study.
The Raw Material:
Patties Part I
Patties Part II
I forgot to mark which ones were mustarded and which ones weren't, could only eat one, and Bow wasn't talking; therefore, our conclusion is that more study is needed.
According to Chris Consentino, who really ought to know,if you cut the meat into strips, as opposed to chunks, it is easier to grind it; Martha Stewart suggests running a bit of bread through the grinder after grinding the now ground meat to clean out the grinding tube. It is grindingly (heyoo) obvious that both grinding tips are correct.