How to Make It
In a colander, toss the cucumber with » teaspoon of salt and let stand until wilted, about 25 minutes. Pat dry.
Meanwhile, soak the guajillo and chipotle chiles in the boiling water until softened, 20 minutes. Discard the stems and seeds and coarsely chop the chiles.
Light a grill. Grill the tomatillos over high heat until they are charred all over, about 5 minutes. Discard the charred skins and coarsely chop the tomatillos.
In a small skillet, heat the 2 tablespoons of vegetable oil. Add two-thirds of the minced garlic and the onion and cook them over moderate heat until softened, about 7 minutes. Transfer to a blender and add the chopped chiles and tomatillos and the cilantro and mint. Puree the sauce and season with salt and pepper.
In a medium bowl, toss the wilted cucumbers with the sour cream, jalapeño, parsley and the remaining minced garlic. Season with salt and pepper.
Brush the trout fillets with vegetable oil and season with salt and pepper. Oil the grate and grill the fish over high heat, skin side down, until the skin is crisp, about 3 minutes. Turn the fish and grill until it is just cooked through, about 2 minutes longer. Transfer the fish to plates and serve with the chile-tomatillo sauce and cucumber salad alongside.