Pan-fry the bacon until crispy. Set aside on a paper towel to drain and then crumble when cooled.
Make the beans: In a small pot, melt the butter and oil over medium heat until hot. Add in the minced garlic and let cook for about a minute (don't let it burn). Add in the beans and cook for about 5-7 minutes until they are heated all the way through. I like to mash them a little with my spatula to make them more like "refried beans". Add in the salt. If they overheat and get too dry, just mix in a tbsp of water.
While the beans are cooking, make the eggs: whisk the eggs and milk together in a bowl (add in a dash of salt and pepper). Scrambled in a non-stick fry pan over medium-low heat until cooked through. You could also fry the eggs if you prefer that! If you are using cheese, you can mix it in with your eggs at the very end so it melts and gets nice and gooey. If you prefer, sprinkle the cheese on top of your tacos while you assemble them
The step before assembling is heating the tortillas- you have a few options here. If you have a gas stovetop, you can place the tortilla right over the small flame for a few seconds until they char a little and flip. You can heat them up in a fry-pan/cast iron skillet. You could also just cover them in a wet paper towel and microwave them for about 15-30 seconds.
Assemble your tacos! Take your tortilla and fill with a generous amount of scrambled egg, beans, crumbled bacon, salsa, avocado, and anything else you like on tacos!