In a cast iron, add oil. When hot, add pork and onion. Cook the pork until browned, but keep slightly pink. Next, drain the fat. When cool enough to handle, use a fork to chop up pork into smaller pieces.
In a large bowl, combine pork, vegetables, egg, soy sauce, and sriracha. Stir well. Let sit for 15 minutes, then drain any excess liquid from mixture.
Next, cut wrappers in half on the diagonal. Place 1 wrapper on a work surface with the longest part of the wrapper closest to you. Add 1 tablespoon of filling on the bottom, spread evenly like a log, leaving a 1-inch space at both ends. Fold the bottom part of wrapper over filling. Begin rolling tightly, about halfway up. Then fold each side piece onto the middle. Then continue to roll, leaving about an inch of wrapper open on the top. Wet top of wrapper with water, and flap over to seal. Continue the same steps with each remaining wrapper and filling. (At this point, you can freeze lumpia wrappers and store for 3 months, if desired)
In a cast iron, heat oil. When hot, add lumpia one at a time. Do not overcrowd the pan. Cook until golden brown, turning often, 2 to 3 minutes. Next, drain on paper towels.
Make the sauce - In a saucepan on medium to high heat, add all ingredients. Bring to a boil, and let sugar dissolve. Reduce heat and let reduce by half. Let cool.
In an airtight container, store in the refrigerator for 1 week.