Open the cans of pinto beans, drain out the liquid and put them into a small pot. Add the chicken broth, garlic, cumin, red pepper flakes, and oregano. Bring to a boil and then turn the heat down to low, so the mix simmers. Simmer for 30 minutes.
About 15 minutes before the beans will be done, beat the egg, milk, salt and pepper together in a small bowl. Put the fish fillets in this egg wash and push them down so they are covered in it.
Put the flour on a plate, and another clean plate next to that one. Take a fish fillet and drag it through the flour until completely covered. Shake the excess flour from each fillet onto the flour plate and move to the clean plate. Repeat until you've done this to all the fillets.
Put the butter and olive oil in a frying pan and turn the heat to medium high. When the butter is melted and sizzling, place the fillets in the pan (don't crowd them, if they won't fit cook in shifts). Give the pan a little shake so the fillets don't stick. Cook for a few minutes, then flip the fillets and cook for a few minutes more. (Sole takes about 3 minutes on each side -- thicker fish will take longer). Take the cooked fish from the pan, put it on a plate, and cut it up into pieces.
Chop the lettuce into strips.
Your beans are hot and flavorful now, turn the heat off.
Warm the tortillas however you prefer (I put them in the microwave two at a time for about 20 seconds on high).
Dole out fish, beans, lettuce, and a spoonful of salsa on each warm tortilla.