Place the chicken breasts in a small glass baking dish. Cover with foil and bake for 40 minutes. Then, remove the chicken from the oven and carefully cut them lengthwise. Bake, uncovered, for 20 more minutes.
Meanwhile, heat 1 teaspoon of the olive oil in a medium-sized frying pan over medium-high heat, and cook the onions until golden brown. In a small saucepan, heat the black beans over low heat with the remaining olive oil.
Remove the chicken from the oven, and with 2 forks, pull the chicken apart. (Do this while hot, so that the pieces pull apart easily.) Transfer to a bowl, and toss with the Cholula.
Place the tortillas in a stack in the microwave, covered with a damp towel, for 22 seconds on high. Then, assemble the tacos, placing the chicken in the shell first, followed by the beans, onions, salsa, and feta.