Preheat oven to 250°F/120°C.
Pat the beef pieces dry with a paper towel and sprinkle liberally with salt and pepper.
To a large oven-proof, heavy saucepan with a lid or Dutch oven, melt the butter and oil over medium heat. Cook the beef in small batches until browned on all sides. Remove and set aside.
To the same pan (add more oil if needed) add the onions and cook until softened, about 5 minutes.
Stir in the garlic, tomato paste and flour, cook for 1 minute (taking care not to brown or burn).
Add the Guinness and stir to deglaze and get any brown bits off the bottom of the pan. Bring to a light boil/simmer until thickened. Stir in the beef and chicken stock.
Add the meat back into the pan along with the carrots, parsnips, thyme, rosemary and bay leaves.
Bring to a light boil/simmer, cover and cook stove top for 1 to 3 hours or you can transfer to the oven for 1 to 3 hours until the meat is fork tender (it should tear apart easily with 2 forks). You can remove the lid for the last 30 minutes to thicken the sauce. Taste for seasoning and adjust.
Remove bay leaves before serving.