For the braised beef
Season the beef pieces with salt on all sides. Heat a braising pot over high heat, add half the olive oil and sear the beef until it develops a nice golden brown color on all sides. Remove the beef from the pot and discard any leftover fat. Place the pot back on the heat, add the rest of the olive oil and sauté the onions and carrots until golden brown. Add the celery and garlic and sauté until the garlic aromas become apparent. Add the tomato paste and cook while stirring for about 2 minutes. Deglaze with the wine and cook until it reduces to a syrupy consistency. Add the demi glace and bring to the boil. Add the beef, thyme and bay leaf, lower the heat, cover and braise over low heat until beef is tender. Alternatively braise in a 140°C oven. Strain the braising liquid and reduce to the desired consistency (taking care to remove the fat as it rises to the top). Combine the beef, the reduced liquid and the separately cooked vegetables and then add the butter and stir to incorporate into the sauce. Check for seasoning and serve.
For the vegetables
Heat the pan over high heat, add 1/3 of the olive oil and sweat the carrot until tender. Season with salt and remove onto absorbent paper. Repeat the process with the other two vegetables.