3 tbsp olive oil
1 tbsp unsalted butter
1 1/2 yellow onions, halved and sliced 1/2 inch thick
1/2 tbsp balsamic vinegar
Salt and pepper to taste
1/4 cup chicken or beef broth
1 tsp corn starch
1/4 cup brown sugar, packed
1/4 cup reduced sodium soy sauce
2 tsp sesame oil
1/2 tsp crushed red pepper flakes
1/4 tsp ground ginger
1 tbsp gochujang (optional)
Green pepper, diced
3 cloves garlic, minced
1 lb ground beef
3 green onions, thinly sliced
Provolone cheese, sliced or grated
4-6 Sesame seed buns
Heat up a cast iron pan on medium heat and add the olive oil, then the butter. Add the sliced yellow onions and cook until caramelized, about 30-40 minutes. Toss with balsamic vinegar and season with salt and pepper to taste.
While waiting prep the sauce. First whisk together cold broth with the cornstarch. In a separate bowl, combine the brown sugar, soy sauce, sesame oil, red pepper, ginger and gochujang if using. Whisk together to combine well.
In a separate skillet, heat up 2 tbsp olive oil on medium heat and add the green peppers. Cook until beginning to brown, then add the ground beef and the minced garlic. Cook beef until well browned, about 3-6 minutes. Drain off fat.
Add the sauce mixture and combine well, then add the cornstarch and broth mixture. Simmer for about 3 minutes, or until it begins to thicken slightly. Add in the green onions and spoon onto buns. Top with provolone cheese and serve.