Preparation

• Combine vinegar, brown sugar, ketchup, chile flakes, and ½ cup water in a small saucepan and bring to a simmer over medium-high heat, whisking to combine until sugar is dissolved. Combine remaining tablespoon water and cornstarch in a small bowl and whisk with a fork to form a slurry. Whisk into sauce and bring to a boil. Allow to cool while you form the crab rangoon.
• Combine cream cheese, crab, and scallions in a medium bowl and fold with a spatula. Lay one wonton wrapper out on a cutting board and place a small amount of filling in the center (about 1 ½ teaspoons). Moisten the edges with a wet fingertip, then seal by either folding it in half in a triangular shape, or by pushing the four edges in towards the center to create a four-pointed star. Transfer to a large plate, cover loosely with plastic wrap, and repeat until all of the filling is used.
• To finish the sauce, add pineapple chunks and puree with an immersion blender or by transferring to a standing blender.
• Heat oil in a wok or Dutch oven to 375°F (190°C). Carefully add 10 to 12 wontons to the oil. Cook, adjusting flame to maintain temperature and agitating and flipping them constantly with a wire mesh spider until crisp and golden brown, about 3 minutes. Transfer to a paper towel-lined bowl to drain, season with salt, and serve immediately with sweet and sour sauce.