Preheat the oven to 375 degrees. Spread the tomatillos on a roasting pan along with half of the onion, the 6 whole garlic cloves, and the jalapenos. Toss with 2 tablespoons of the oil and season with salt and pepper. Roast for about 35 minutes, until tender.

Transfer the vegetables to a blender and puree until smooth. Add the lime juice, chopped cilantro and 2 tablespoons of the honey and pulse to blend. Season the tomatillo salsa with salt and pepper and transfer to a bowl. Rinse out the blender.

In a medium saucepan, heat another 2 tablespoons of the oil. Add the chipotle, cumin, chopped garlic, and the remaining onion and cook over moderate heat, stirring occasionally, until the onion is softened, about 5 minutes. Add the beans with their liquid and 1/4 cup of water and cook over low heat for 15 minutes. Transfer the black bean mixture to the blender and puree until smooth. Season the sauce with salt.

Light a grill or preheat a grill pan. In a small bowl, combine the remaining 2 tablespoons of honey with the ancho chile powder and mustard and season with salt. Brush the salmon with oil and season with salt and pepper. Grill the fish skin side down over moderately high heat until very crisp, about 3 minutes. Cook the fish on the remaining 3 sides just until lightly charred, 3 minutes longer. Brush the salmon with the chile-honey glaze and grill skin side up until lightly caramelized, 2 minutes.

Spoon the tomatillo salsa on plates and top with the salmon. Garnish with sour cream and the cilantro sprigs and serve with the black bean sauce.