"Regular or spicy mustard?" the counterman asked.
I thought for a moment and answered "Regular," since I felt that was less likely to contain some interesting adulterant that I'm allergic to.
When the sandwich came, I found it had dijon mustard on it.
In what universe is dijon mustard "regular" mustard?
I normally avoid dijon mustard because it contains small quantities of sulfites which I'm allergic to. Fortunately, my sulfite load was low enough that the sandwich didn't set me off.
However, dijon mustard on pastrami is really pretty revolting.