Using up the last two slices of bread in the house, I just wolfed down a dee-licious homemade egg sandwich. No cheese or breakfast meats, just two eggs w/salt & pepper on toast with butter and a thin layer of mayonnaise and brown deli mustard on each side.
OMG, so good. I would make another, but...WE'RE OUT OF BREAD!!!
I've been trying to remember when I started with the mayo and mustard, but I think I was doing it as far back as the early '80s in California. Many will say "mustard?!?". Lordy, yes, bring it on. Nathan says that's a strong Pennsylvania Dutch (Deutsch) influence, as they put mustard on everything including eggs, which they pronounce "ecks".
This puts me in the mood to shop for a complete set of foodstuffs for Northeastern Diner/Deli Style breakfast sandwiches. But honestly, at home they can become a lot of work. Oh, it's easy enough to add a slice of cheese, but the simple fix above is quite enough.