Add the olive oil into a pressure cooker, season the roast with salt and pepper; brown on all sides over high heat.
Remove the roast from the heat and set aside on a plate. Add the garlic, white wine and chicken stock to the pressure cooker. Heat over high heat scraping the bottom to get the juices.
Put the roast back into the pressure cooker, close and cook for 45 minutes after it starts whistling.
Carefully open the pressure cooker after the steam has gone and add the onion and fennel then close the cooker again. Cook for 20 minutes after it starts whistling.
Remove the roast and vegetables from the pressure cooker and keep warm. Put the pressure cooker on the stove without the lid and reduce the sauce for several minutes. If it is too liquid you can add a tablespoon of flour to thicken the sauce stirring constantly.