How to Make It
In a large heavy skillet, heat 1 tablespoon of the oil over medium high heat until hot, then stir in the garlic and cumin, and cook, stirring, until golden, about 2 minutes. Stir in the black beans and 1/4 teaspoon each pepper, and stir to combine. Let the black bean mixture cool to warm.
Place each chicken breast, smooth-side-up, on a work surface. Place the palm of one hand on top of one breast, then insert a pairing knife to make a length-wise pocket in each breast. Divide the black bean filling between the breasts, stuffing them full. Reserve any leftover black beans to serve on the side. Rub the chicken with the remaining 1 tablespoon oil, then season all over with 3/4 teaspoon salt and 1/2 teaspoon pepper.
Preheat the oven to 425°F.
Place the chicken breasts on an oiled baking sheet and bake until cooked through, about 30 minutes. Let stand 5 minutes before slicing and serving with the cilantro.