Beat and whisk an egg in a bowl. Set aside.
Separate the whole amount of shrimp into 2 equal parts. Place one half into a food processor, and add salt, pepper, chili flakes, paprika, garlic and cilantro. Finely chop.
Cut the other half of the shrimp into 1/5 pieces.
Transfer all the shrimp to a bowl, and add cornstarch and 1 tbsp of the beaten egg. Mix well.
With your hands, shape two burger patties. Place them on the plate line with an oiled baking sheet and chill for 30 mins.
Cut the arugula stems out, we will use only leaves in the burger. Peel and cut half of the red onion into semi-circles. Slice the cheese. Set everything aside.
Peel the pineapple, cut it into circles 0.8-1cm thick and delete its core. Grill the slices on medium heat with some olive oil or butter for about 30 sec on each side or till they get grill strips and get softened. Set them aside.
Preheat your oven to 180°C (356°F). Prepare 3 bowls: flour is in the first, the remaining beaten egg is in the second, and panko crumbs are in the third.
Coat the patty with the flour first, then dip it in the beaten egg mixture. Finally, cover it with panko crumbs, pressing to adhere.
Transfer both patties on the baking tray lined with baking paper and drizzled with oil. Bake for 5 mins in the oven, then turn the patties to the other side and bake for 5 mins more till golden color. After 10 mins place the cheese on the patties and bake 3-4 mins more, till the cheese is melted. Total baking time is 13-14 mins.
Fry the buns on the pan with some butter till crispy and golden.
Assemble the burger. Spread some sweet-n-sour sauce on the inner parts of the buns. Place the shrimp pattie with the cheese on the bottom bun. Sprinkle it with chili sauce (optional). Then place 2 pineapple slices, red onion and arugula leaves. Cover it with the top of the bun. Enjoy!