Mongolian Meatball Cabbage Cups

large cabbage leaves, quartered

ground beef

panko bread crumbs

green onions, thinly sliced, divided

egg

cloves garlic, minced

sesame oil, divided

Kosher salt

Red pepper flakes

vegetable oil

minced ginger

low-sodium chicken broth (or water)

low-sodium soy sauce

brown sugar

large carrot, peeled and thinly sliced

Sesame seeds, for garnish