Combine the lemon, parsley, garlic, oil and salt in a blender until mostly smooth.
Toss the chicken with the gremolata and marinate overnight or for at least 4 hours.
Preheat the oven to 350°F.
Remove the chicken from the marinade, discard marinade and season chicken with salt and pepper. Roast on a baking sheet until cooked through, about 22 minutes.
In a large pot, bring the water, milk, butter and salt to a boil. Reduce heat to low and whisk in the polenta. Cook, stirring regularly, for 20 minutes. Fold the corn and cheese into the polenta and cook for 10 more minutes. Season with salt and pepper.
To make the salsa, place the tomatoes, jalapeño, garlic, onion and ancho chile on a sheet pan. Toss with oil, salt and pepper and roast for 15 minutes. Transfer the vegetables to a blender, along with the chipotles in adobo sauce, cilantro, cumin, red onion and water. Blend until mostly smooth, with a few chunks.
Toss the asparagus with the oil, salt and pepper on a baking sheet. Roast for 10-12 minutes, until crisp-tender.
To serve, divide the polenta between plates. Top with chicken, asparagus and salsa.