Mexican leftovers are the best, because they make the best breakfasts.
Most people think of beans on toast as crappy British food, but believe it or not there's a Mexican equivalent which is absolutely delicious.
Molletes are toasted open-face "sandwiches" of refried beans topped with melted Mexican cheese, salsa, and anything else you like.
The popular salsa choice would be classic chunky tomato and chile salsa, but I didn't have any so I used some Cholula.
I did, however, have some homemade refried black beans.
Molletes are usually made with bolillo, which is like a baguette, but I had some sourdough, which is more like Mexican birote, to use up.
I heated the beans up, toasted the bread, then topped the bread with the beans and some cheese.
Queso Chihuahua is a good melting cheese for this dish, and you can get it from Gringa Dairy. Otherwise some medium white cheddar will do.
Put the molletes under the grill to melt the cheese if you wish, then add the other condiments.
I used some leftover white picked onions (a white onion version of Yucatecan cebollas en escabeche).
You can use any kind of refried beans for this, and it's apparently very popular with Mexican businessmen.