Combine the soy sauce and gochujang, rice syrup, gochugaru (or gochugaru), mirin, sesame oils, and black pepper in a bowl. Mix all things together until it is completely dissolved.
Add the whisked liquid marinade ingredients to the bowl along with the pear, garlic and ginger to a food processor
The food processor should be pulsed 10-15 times until all ingredients are combined into a liquid. You can taste test the marinade, and adjust it if necessary. NOTE: This recipe has a mild spice level. You can adjust it after tasting. You can add more gochugaru or gochujang to make it more spicy. To add more sweetness, you can add more rice syrup. You can also add more soy sauce to increase the saltiness.
Add the pork slices, yellow onions, and green onions to a large bowl. Use your hands or tongs to coat all the meat with the marinade.
Place the marinated meat in an airtight container. Refrigerate for at least one hour. Place the meat in a container and let it cool on the counter for at least 20 minutes.
Add the vegetable oil to a cast iron skillet on medium heat. Continue to stir the meat until it is well coated.
My 12" cast iron skillet only held 1/3 lb of meat at one time. This allowed the meat to brown slightly towards the end. Before you cook the next batch, it is possible to have to clean or scrape the pan of any burned bits.
Take out of the pan immediately and serve.