Preheat oven to 300 degrees Fahrenheit. Heat oil in a roasting pan or Dutch oven over medium heat. Season ribs with salt and pepper. Add ribs to the pan and sear until browned on all sides. Remove ribs and set aside. Add sweet onion to the pan and cook until translucent, about five to seven minutes.

Add ribs back to the pan. Pour Guinness and beef stock on top and bring to a simmer. Cover and transfer to oven. Bake for two hours. Remove from oven and add cipollini onions. Return to oven and bake for one additional hour. Remove from oven and shred meat using two forks. Season with additional salt and pepper.

Raise oven temperature to 350 degrees Fahrenheit. Place ramekins on a baking sheet. Using a slotted spoon, spoon filling into ramekins. Cover with a sheet of puff pastry. Using a pastry brush, brush egg wash over puff pastry. Bake until pastry is golden and puffy, about 20-24 minutes.