Preheat your oven to 425°F and line a small baking sheet with parchment paper.
Remove the husks from the tomatillos, rinse them to remove the sticky residue, and place them on the baking sheet with the jalapeño, onion, and garlic cloves.
Drizzle the vegetables with half of the olive oil and roast for 15 minutes until they are softened and slightly charred.
While the vegetables roast, season the chicken breast with sea salt, black pepper, and the remaining olive oil, then sear in a hot skillet for 5-6 minutes per side until fully cooked.
Transfer the roasted tomatillos, jalapeño, onion, and garlic into a blender along with the avocado, cilantro, and lime juice, then pulse until smooth and creamy.
Slice the seared chicken breast into strips and serve it in a bowl generously smothered with the warm, creamy salsa verde.