1) Add chicken breasts to a medium pot and cover with water by 1/2 inch. Bring to a simmer and simmer for about 15 minutes or until chicken is cooked through.
2) Once chicken has cooled a bit, shred it. Also, dice onion and pepper and drain and rinse the beans.
3) Add 2 tablespoons olive oil to a medium pan over medium heat. Once hot, add onions and peppers and cook until soft. Then stir in shredded chicken, black beans, and salsa.
4) Stir mixture until it’s heated through and season with salt and pepper.
5) On a large griddle or in a large skillet, add a tablespoon of olive oil over medium-high heat. Working with one tortilla at a time, add it to the hot pan and top one half with chicken and shredded cheese. Fold tortilla over to form a taco. Press down on it lightly so it holds it’s shape and move it to the outer part of the pan while you work on a second one. Do as many tacos as you can fit at once without them overlapping.
6) Cook tacos for about 3 minutes per side until tortilla is crispy and cheese is well-melted.
7) Serve tacos immediately with avocado, hot sauce, lettuce, and sour cream.