Preheat oven to 325°F (160°C). Season the short ribs generously with salt and pepper.

In a Dutch oven over medium-high heat, add vegetable oil. When shimmering, sear the ribs for 3–4 minutes per side until deeply browned. Transfer ribs to a plate.

Reduce heat to medium, add sliced onion and smashed garlic to the pot. Sauté until softened, about 5 minutes, scraping up brown bits.

Pour in stout beer to deglaze, stirring to lift any fond. Let the beer reduce by half, about 3 minutes.

Stir in beef broth, thyme, and rosemary. Return short ribs to the pot, nestling them into the liquid.

Cover Dutch oven, transfer to the preheated oven, and braise for 2 hours until meat is fork-tender.

Remove ribs and herbs, skim excess fat from the surface, and simmer sauce on stovetop if you prefer a thicker gravy.

Serve ribs drizzled with sauce and garnish with chopped parsley.