Puffy Chicken Taco

recipe source: saveur

¼ cup olive oil
2½ lb. bone-in, skin-on chicken thighs

Kosher salt and freshly ground black pepper, to taste
6 cloves garlic, finely chopped
1 medium yellow onion, finely chopped
1 rib celery, finely chopped
1 small carrot, finely chopped
1 small red bell pepper, finely chopped
3 cups chicken stock
1 14-oz. can whole peeled tomatoes in juice, crushed by hand
2 avocados, pitted, peeled, and mashed
2 cloves garlic, minced

Juice of 1 lime

Canola oil, for frying
3 cups masa harina (available from Amazon.com)
1½ tbsp. unsalted butter, softened

Shredded iceberg lettuce, diced tomato, and shredded cheddar cheese, to garnish

Heat oil in an 8-qt. saucepan over medium-high heat. Season chicken with salt and pepper, and add to pan, skin side down; cook, turning once, until browned on both sides, about 8 minutes. Transfer chicken to a plate; set aside. Add garlic, onion, celery, carrot, and bell pepper; cook, stirring, until soft, about 20 minutes. Add stock and tomatoes, and return chicken to pan; bring to a boil. Reduce heat to medium-low; cook until chicken is very tender, about 1½ hours. Remove chicken from sauce, and let cool; reserve sauce for another use. Discard skin and bones, and shred chicken; set aside. Meanwhile, combine avocados, garlic, lime juice, and salt and pepper in a bowl; chill guacamole until ready to use, covering to avoid browning.  Pour oil to a depth of 2″ in a 6-qt. Dutch oven and heat over medium-high heat until a deep-fry thermometer reads 375°. Stir together masa, butter, and 2¼ cups warm water in a bowl until dough forms; divide dough into 12 pieces and shape each piece into a ball. Using a tortilla press or rolling pin, flatten each ball into a 6½″ disk. Place 1 disk in oil. When it begins to puff, press the end of a metal spatula into the middle of the tortilla so that tortilla bends into a taco shape; hold spatula within tortilla until taco is golden brown and crisp, about 1½ minutes. Transfer taco to paper towels to drain; repeat with remaining tortillas. Divide chicken and guacamole among tacos; top with lettuce, tomato, and cheese.