Make the Quick Pickled Red Onion: Place the sliced red onion in a small bowl. Add the vinegar, sugar, salt and pepper. Stir to combine. Cover and let stand at room temperature while you make your flautas.
Add the cooked chicken to a skillet over medium-low heat. Pour salsa over-top, then the water. Stir to combine. Cover the skillet and allow the chicken to warm with the salsa and water for 4-5 minutes. (The water should have been absorbed. If not, cook uncovered for a minute or so to cook it off). Remove the chicken mixture to the bowl of a stand mixer fitted with a paddle attachment (or alternately just in a bowl with two forks). Run the mixer on low for a minute or two to shred the chicken. Set aside.
Place a large tortilla on a cutting board. Cut the rounded edges off from each side, making a rectangle (see Step by Step photos above the recipe card). Place a row of the shredded chicken down the centre of the rectangle, then roll the tortilla up around it, rolling from the longer side. Place it seam side down, so it doesn't un-roll. Repeat with the remaining tortillas.
Heat a 1/2 inch of oil in a skillet over medium-high heat. (I like to cook just one at a time, in a small skillet. They cook up quickly and you don't need as much oil to get the 1/2 inch in a smaller skillet). Add one of the rolled tortillas to the skillet, seam side down. Allow to cook about 30- 45 seconds, then begin rolling it a quarter turn and allowing it to brown a bit before rolling it a quarter turn again, until the tortilla is evenly golden all around. Remove to a cooling rack and repeat with the remaining rolls.
While flautas are cooking, take a moment to stir together the sour cream and cream for the crema. Set aside.
Place warm flautas on a platter. Top with topping ingredients, placing them in the order listed in the ingredients, finishing with a drizzle of the crema. (*I love to generously add the toppings, almost to the point you can hardly see the flautas.)
Notes
1. Use left-over cooked chicken or chicken from a rotisserie chicken. Alternately, start with fresh chicken, start with 2 large boneless, skinless chicken breasts. Cut each in half lengthwise, then cut each of those pieces in half across the middle, making 8 smaller pieces from the 2 breasts. Place in a skillet and cook over medium heat until they are no longer pink on the outside. Add the salsa and water, cover the skillet, reduce the heat and cook another 5-10 minutes, or until the chicken is cooked through and soft. The water should be absorbed, but if it's watery, cook uncovered for a minute or so to cook it off. Proceed with shredding the chicken per the recipe.You can bake the flautas instead of frying. Brush the rolls lightly with a bit of cooking oil (or spray with cooking spray), place on a baking sheet and bake in a preheated 375F oven for 15-20 minutes, or until crisp.To air fry the flautas, preheat your air fryer to 385F. Brush the tops of the rolls with a bit of cooking oil (or spray with cooking spray) and place shaped flautas into the air fryer (in a single layer with a bit of space in between), seam side down. Air fry for about 8 minutes, flipping the flautas over halfway through cooking.Flautas can be re-heated on a baking sheet in a 350F oven for 8-10 minutes, or until warmed.