Heat the oil in a frying pan over a medium heat. Add the onion and garlic and fry for 4-5 minutes, or until softened but not coloured. Add in the chopped mushrooms and cook for just 2 minutes more. Mix together the parsley, thyme, Maltese sausage meat, llemon zest and lemon juice in a bowl until well combined. Add the cooked onion and garlic and the egg yolk and stir well to combine. Season, to taste, with salt and freshly ground black pepper. Lay each piece of thigh meat out and spread with an even layer of the stuffing mixture. Roll up each stuffed chicken thigh and tightly wrap around 2 slices of streaky bacon. Place each stuffed chicken thigh into a roasting tin and dot all over with butter. Roast the stuffed chicken thighs in the oven at 180`c for 35-40 minutes, or until cooked through and the bacon is crispy. When ready, remove the chicken and allow to rest. Add the chicken yeast extract to the juices and mix well to form a sauce. To serve, cut the stuffed chicken thighs down the middle diagonally and serve with roasted vegetables and potatoes and the glossy chicken sauce.