The best sandwich I ever had was a panini I randomly threw together for a snack at three in the morning. The next day I went to make it again since it was so delicious, but realized I'd forgotten some of the ingredients I used. I was in the middle of a sandwich-making phase at the time so I had like a dozen types of bread, meat, and cheese to pick from.

This was a decade ago and I've never been able to recreate that perfect sandwich despite several attempts. It's my culinary white whale. The only ingredients I am sure of are the spread (light mayo in one side, applewood-smoked bacon mustard on the other) and the meat (honey-smoked turkey), and that it was only a simple meat-and-cheese. The bread and cheese continue to elude me.