I was making Caesar Salad last night and managed to split the mayonnaise while making it – this is pretty easy to do if you add too much oil too fast. The simple way to fix this problem is just to start again with a new egg and slowly whisk back in the split mayonnaise – the only requirement for this rescue is that you have an extra egg.
Of course as fate would have it I had no more eggs. At this point I was faced with making an emergency trip to the shops to buy more eggs, but then it occurred to me to see if I could rescue the split mayonnaise with dijon mustard. I tipped out the split mayonnaise, added around a teaspoon of dijon mustard to the jar, and then slowly added back the split mayonnaise while whisking the whole time. Thankfully it worked and I ended up with nice unsplit mayonnaise. The flavour was not too bad either.