Season the short ribs on all sides with the kosher salt and black pepper. Heat a large Dutch oven over medium high heat. Add in the short ribs and cook for 2-3 minutes on each side until a golden brown crust develops. It doesn't have to be cooked all the way through. Remove the short ribs from the pan and set aside.
Reduce the heat to medium and add in the vegetable oil. If you have a lot of grease left in the pan from the short ribs you can skip the vegetable oil. Use paper towels to absorb the grease until there's only about 1 tablespoon of it left. Mix in the onion and sauté for 2-3 minutes until it turns translucent. Add in the ginger and garlic and cook for 30 seconds. Mix in the turmeric, coriander, cinnamon, allspice, chili flakes, cumin, and bay leaf. Cook for another 30 seconds.
Pour in 5 cups of the vegetable broth followed by the sweet potatoes. Mix and make sure to scrape up any bits stuck to the bottom of the pan. Add the short ribs back into the pan. Increase the heat to medium high and bring the broth to a bubble. Reduce the heat to low and gently simmer for 3½ - 4½ hours until the short ribs are tender. Stir every so often.
When the short ribs are tender, remove them from the pan. Discard the bay leaf. Scoop up the leftover sweet potatoes and broth and add them into a blender. Pour in the remaining 1½ cups of vegetable broth into the blender. Blend until smooth. Pour the sauce back into the pan and and heat over medium heat. Mix in the coconut milk and brown sugar. Taste the sauce for seasoning and adjust with salt and pepper if needed. Once the sauce is heated through turn off the heat.
Ladle the sauce into the serving bowl. Nestle in the pieces of short ribs. Garnish with cilantro leaves and toasted sesame seeds. Enjoy!