Mixing the burgers: In a large mixing bowl, add ground pork. Add fish sauce, soy sauce, sriracha, red curry paste, ginger, cilantro, mint, lime zest, sesame oil, salt, black pepper, lemongrass powder and garlic. Mix with hands until well combined. Take care to not overmix the hamburger meat.
Making the burger patties: You will form 7-8 burgers out of the meat. Portion the meat into equal amounts for each burger you will be making. To make the patty, take the burger meat and press down in between the palms of your hand to flatten. Continue to flatten while turning the meat until a circular shape is reached. The burger patty should be roughly 3/4 inch thick on the outside. Try to have the middle at about 1 inch thickness.
Cooking the burgers: Heat a pan sprayed skillet on medium heat. When the pan is hot, add the burger patties. Do not add more than 4 patties to the pan so that you don't overcrowd the burgers. Fry for 5-6 minutes, flip and cook for an additional 5-6 minutes or until cooked through. Once the first batch is cooked, transfer to a paper towel lined plate. Repeat with the second batch.
Making the peanut sauce: Heat a small pan sprayed saucepan on medium heat. Whisk all ingredients continuously for 5 minutes until fully combined and a creamy, smooth texture is reached.
Toasting the buns: While frying the burgers, heat a separate pan sprayed frying pan on medium heat. Each set of buns will use roughly ½ tablespoon of butter. Slather the desired amount of butter on each side of the buns. You will grill your hamburger buns, top and bottom for about 1 minute on each side or until golden brown.
Assembling the burgers: When ready to assemble each burger, spread 1-2 tablespoons of the Peanut Sauce on the top and bottom buns. Place the Thai pork burger on the bottom bun. Top the burger with layers of sprouts, bok choy, purple onion and (optional) Thai chilis. Cover with the top bun and serve.