Step 1In a blender, combine the lime zest and juice, water, onion, garlic, vanilla, ginger, chipotle powder, soy sauce and serrano chile. Blend until well pureed.
Step 2Place the trimmed wings in a large, sealable plastic bag. Pour over the marinade and eliminate as much air as possible before sealing the bag. Use your hands to massage the marinade through the bag over the wings. Refrigerate at least 4 hours, up to overnight.
Step 1In a medium saucepan, combine the peanut butter, brown sugar, canola oil, sesame oil, Key lime juice, salt and chipotle powder. Heat the mixture over medium-low heat, stirring frequently, until the ingredients are combined and the sauce warms; be careful not to overheat or the sauce may burn. Taste the sauce and adjust as needed (with extra brown sugar, sesame oil, Key lime juice or salt). Remove from the heat and set aside in a warm place. This makes about 1 1/3 cups sauce.
Step 2Remove the wings from the marinade, wiping off the excess marinade with paper towels to dry the wings.
Step 3Fill a 4-quart pot with frying oil to a depth of 3 to 4 inches. Heat the oil to maintain a temperature of 350 degrees. Meanwhile, heat the oven to 375 degrees.
Step 4Fry the wings, in batches, until the meat is firm and opaque, and the skin is crisp and a rich golden-brown, about 5 to 7 minutes. Remove the wings to a large rack on a baking sheet, spacing them at least 1 inch apart from each other. Continue until all the wings are fried.
Step 5Brush each wing on one side with a light coating of sauce. Place the wings in the oven for about 3 minutes to bake the sauce onto the wings. Remove the wings from the oven and flip them over, brushing the other side with a light coating of sauce. Sprinkle over the sesame seeds and bake again for about 3 minutes.
Step 6Remove from heat and allow to cool just slightly (enough so they can be handled). Meanwhile, thin the remaining sauce if desired with a little extra canola oil, then pour it into a small bowl and garnish with the chopped green onion.
Step 7Remove the wings to a plate or platter and serve immediately, with extra sauce on the side.