Roast Beef and Fried Egg Sandwich

Saturdays my mom often made a breakfast style meal for supper, along with a cup of tea. I learned how to make this Sandwich in Grade 8 Home Economics class. Do they still have those classes in school today? I was so impressed that I learned something new and it was something I could actually make for my family, I made it that very weekend. A great way to use up leftover roast beef.
I will give you the list of ingredients, and you make your sandwich according to how many you are feeding. For one sandwich you need the following -

toasted bread or bun of your choice
mayonnaise
your favorite mustard
1 small onion, caramelized (thinly sliced and fried slowly on low heat in a bit of butter or oil until you have a deep brown color)
1 fried egg
leftover roast beef or store bought sliced cooked roast beef that you can purchase at the deli counter
cheese

Voila, with some pickles on the side that is all you need. Enjoy.