Heat your grill to high.
Stir together the ancho powder, pasilla powder, cumin, coriander, ginger, brown sugar, garlic powder, onion powder, allspice, cinnamon, cloves, fennel, chile de arbol, 2 tablespoons salt, black pepper and cayenne in a small bowl.
Brush both sides of the breasts with the oil and season with salt. Rub the top side of each breast with a few tablespoons of the rub and place on the grill, rub side down. Grill until golden brown and slightly charred, 3 to 4 minutes. Turn the breasts
over and continue grilling until just cooked through, 4 to 5 minutes longer.
Remove the chicken from the grill and drizzle with the black pepper vinegar sauce. Tent loosely with foil and let rest for 5 minutes. Serve the slaw on the side.
Black Pepper Vinegar Sauce:
1/4 cup rice wine vinegar
1/2 cup extra-virgin olive oil
3 tablespoons Dijon mustard
2 teaspoons honey
1 teaspoon kosher salt
3/4 teaspoon coarsely ground black pepper
Combine the vinegar, oil, mustard, honey, salt and pepper in a blender and blend until smooth. The sauce can be made 1 day in advance, covered and refrigerated. Bring to room temperature before serving.