Heat second tablespoon oil in the same Dutch oven. Add onion and carrot and season with salt and pepper. Cook, stirring occasionally, for 8 minutes. Add garlic and cook 2 more minutes, until garlic is fragrant. Add molasses and stir to combine. Pour in apple cider and scrape up any brown bits stuck to the bottom of the pot. Put short ribs back in the pot over vegetables. Pour beef broth over ribs. Add thyme sprigs. Cover and bring to a simmer over high heat.