Add the minced / ground beef to a bowl along with the onion, parsley, dijon mustard, egg and breadcrumbs. Season well with salt and pepper and using your hands, bring all the ingredients together so they are well combined.

Mould the meatballs by taking a small amount of the mixture and roll in to small balls in the palm of you hand (you should be able to make around 20 balls depending on size), try to make them about the same size, but don't worry too much if some are a little larger than others.

Heat the olive oil in a casserole or sauté pan add the meatballs and season again with a good pinch of salt and black pepper and keep turning until lightly browned on each side. Remove meatballs from the pan and set aside.

Over a medium-high heat, add the butter and allow to melt, then stir in the onions and allow to soften slightly. Add the mushrooms and thyme and cook for a further few minutes until the mushrooms are tender, golden brown and no longer release any water.

Stir in the plain/all-purpose flour, and allow to cook for a minute, making sure the flour is well mixed with the other ingredients, then pour in the stock, add the Worcestershire sauce and tomato puree and stir to combine.

Add the meatball back to the pan, and cook with the lid on for 15 - 20 mins minutes or until the meatballs are cooked through.

Finally, remove the meatballs, taste the sauce and adjust the seasoning. Serve the meatballs with the gravy spooned over the top and a sprinkle of flat leaf parsley.