1. Preheat the oven to 450 degrees F. Toss the sweet potato slices in 3 tablespoons oil and sprinkle with salt and pepper. Lay the slices in a single layer on 2 baking sheets and roast until brown and beginning to crisp, 20 to 25 minutes, flipping the slices halfway through.
2. Meanwhile, in a medium nonstick skillet over medium-high heat, cook the chorizo in the remaining 1 tablespoon oil until browned, 3 to 5 minutes. Transfer to a paper towel-lined plate to drain.
3. Put the avocado, onion, lime juice, serrano, and cilantro in a food processor and pulse until smooth. Season with salt and pepper, and then pulse a few more times.
4. Top the sweet potato slices with the chorizo and shredded cheese; return to the oven to melt the cheese. Serve topped with the avocado salsa and a cilantro leaf garnish.
Copyright 2011 Television Food Network, G.P. All rights reserved