1 1/2 pounds chicken breasts or pork tenderloin, cut into 1/2-inch to 1-inch pieces
1 each green and red bell pepper, seeded and cut into 1/2-inch pieces
2 cups pineapple chunks (optional)
Peanut oil, for frying
For the frying batter:
1/2 cup all-purpose flour
1/2 cup cornstarch
1 teaspoon kosher salt
1/2 teaspoon baking soda
2 egg whites
2 tablespoons canola oil
1/3 cup (5 tablespoons) warm water
For the sweet and sour sauce:
1/2 cup rice vinegar
1/4 cup plus 2 tablespoons brown sugar
1/4 cup ketchup
1/4 cup pineapple juice
1 tablespoon cornstarch, dissolved in 1 tablespoon water
1/2 teaspoon soy sauce
Preheat sous vide to 130 degrees F
Cut pork tenderloin into 2 pieces then season with salt and pepper
Vacuum seal the tenderloin and cook sous vide for 2 hours
Heat a couple of tablespoons canola or vegetable oil in a heavy dutch oven over medium-high heat. Sauté the bell peppers and pineapple until tender, about 6 to 8 minutes. Remove the vegetables from the pan and set aside.
Combine the flour, cornstarch, salt, and baking soda in a large bowl. Add the egg whites, canola oil, and water and whisk until the mixture is thick and sticky (almost glue-like). Stir the marinated chicken into the fry batter until every piece is completely coated.
Working in batches, fry the chicken until crisp and golden brown, about 1-2 minutes per batch. The coated chicken pieces will want to clump together in the oil, so I like to put in each piece one by one. The oil temperature will drop to approximately 350°, which is the temperature you should maintain while frying. Be sure to adjust the heat accordingly.
Using a spider, remove the cooked chicken to drain on a sheet pan lined with paper towels or a large brown paper bag. Return oil to 375° before continuing on to the next batch. When all the chicken is fried, return oil to 375° and begin the sweet and sour sauce.
Combine the rice vinegar, brown sugar, ketchup, pineapple juice, cornstarch slurry, and soy sauce in a small saucepan. Cook over medium heat, stirring occasionally, until the sauce begins to gently boil. It will darken in color and become thick. Immediately reduce heat to simmer and keep warm.
Meanwhile, add all of the fried chicken back into the hot oil for about 30 seconds to 1 minute. The second fry will not only re-heat the chicken but make it extra crispy. Remove the chicken back to the sheet pan lined with fresh paper towels or a large brown paper bag. In a large bowl, toss the hot chicken with the warm sweet and sour sauce and reserved vegetables. Serve immediately with cooked white rice or noodles.