Make the sweet and sour sauce. Add ketchup, pineapple juice, vinegar, chicken broth, soy sauce, and brown sugar to a saucepan over medium heat. Bring to a boil, whisking occasionally. Boil for 20-25 minutes, until the sauce reduces by about 50%.
Whisk together cornstarch and water into a small bowl to create a slurry. Reduce the heat to low heat and add the slurry to the sauce and stir together until the sauce thickens and has a syrup-like consistency (about 3-5 minutes). Add butter and whisk until butter is melted, then set aside to cool.
Now make the crab filling. Combine cream cheese, crab, diced scallions, Worcestershire sauce, soy sauce, onion powder, garlic powder, and sugar in a large bowl. Mix together.
Fill a small bowl with water. Lay 1 wonton wrapper out on a cutting board and add about 1/2 tbsp of creamy crab mixture into the center of a wonton wrapper. Dab your index finger in the water and run your finger along the edges of the wonton wrapper.
Grab the edges of the wrapper and pinch together to make a four-pointed star. Gently press to seal together and place onto a large plate. Cover with plastic wrap or a damp paper towel so that they don’t dry out and repeat with remaining wrappers/filling.
In a large pot, heat oil to 360-375 degrees F. (you'll need about 3 inches of oil) Deep fry 8-10 crab rangoons at a time, until golden brown, about 2-3 minutes, flipping halfway through.
Remove from the hot oil with a slotted spoon and transfer to a paper towel lined bowl to drain any excess oil. Sprinkle with flaky salt. Garnish with chopped green onions and serve with sweet and sour sauce.
Notes
Chop the crab finely! Whether using imitation crab or real crab, chop it into small pieces so you get crab in every bite without big chunks tearing the wrapper.Don’t overfill the wonton wrappers! A half tablespoon or so of filling is plenty; too much makes them burst while frying.Fry in batches! Overcrowding lowers the oil temp and makes the wontons soggy.Seal well - use water around the edges andpress out any air bubbles. This also prevents the filling from leaking out while frying!