I knew someone would ask this particular question.
Firstly, I never run out of mustard.
However, in the hypothetical scenario I did, the first order of business would be to calm my dog down - he is highly protective of his sausages and if someone is after the mustard, he would know what was coming next.
Yeah. That's good advice. Much easier to calm the pet down than trying to get the random intruder to relax.
There is no hope for the intruder - they don't have mustard.
I keep some by the door just in case.
A wise move.