Korean BBQ Burger

Name: Korean BBQ Burger
Ingredients: 1/2 c. (plus 1 tbsp.) soy sauce; 1/4 c. brown sugar; 1 1/2 tbsp. sriracha; 2 cloves garlic, minced; 2 tsp. ginger; 2 tbsp. (plus 2 tsp.) rice vinegar; 2 tsp. crushed red pepper flakes; 1 tbsp. cornstarch; 1 tbsp. water; 1 c. Napa cabbage, shredded; 1 purple cabbage, shredded; 1 jalapeño, seeded and thinly sliced; 1/4 English cucumber, thinly sliced; kosher salt; 1 lb. ground short rib (other ground beef can be substituted); 2 tbsp. unsalted butter; 3 sesame seed hamburger buns