Preheat the broiler to High.

Place the tomatillos on a lined baking sheet and broil for 10 minutes, turning halfway through. Remove and place in a blender or food processor with avocado, jalapeño, garlic, lime juice, agave, and greek yogurt. Process until smooth. Taste and season with salt and pepper to taste. Set aside in the refrigerator until ready to use.

Preheat the oven to 425˚F. Line a rimmed baking sheet with silicone mat or aluminum foil. Set aside.

Heat 1 Tbsp oil in a medium skillet over medium-high heat. Once hot, add onion. Cook, stirring occasionally, until softened, about 2 to 3 minutes.

Add chicken and taco seasoning, stirring to combine. Remove from heat and set aside.

Wrap the corn tortillas in damp paper towels. Microwave on High for 30 seconds to 1 minute, until pliable. Keep the tortillas wrapped in the towels as you assemble the tacos.

Brush both sides of each tortilla with oil. Place on the prepared baking sheet.

Sprinkle the tacos with a little cheese on half of each tortilla, using half of the cheese. Top with the chicken, dividing evenly between the tortillas. Sprinkle with remaining cheese. Fold the tortillas, creating the tacos.

Bake for 8 to 10 minutes. Remove the pan from the oven and carefully flip the tacos. Bake for another 8 to 10 minutes, until golden brown and the edges are a dark brown.

Sprinkle with cilantro and serve with avocado tomatillo sauce.