Place 600g of gravy beef in a bowl. Add the flour and toss using your hands to coat. Pour olive oil in a pan over high heat. Cook the meat until brown, turning using a wooden spoon. Repeat in four batches. Add onion and pancetta and cook until soft. Transfer to a separate bowl. Add mushrooms to the pan and cook, stirring until tender. Add garlic and continue to stir. Return beef and the onion mixture to the pan. Pour in a can of beer then add stock, tomato paste, thyme, bay leaves and rosemary. Bring to the boil. Cook covered for 1½ hours, stirring occasionally. Remove lid and cook for 30 minutes. Spoon into four ovenproof dishes.
How to make the potato topping:
Place thinly sliced potato in a large bowl then pour over melted butter. Sprinkle over sea salt and thyme then use fingers to toss. Layer one-quarter of the potato mixture on a tray lined with baking paper to form a round stack, about 12cm in diameter. Repeat with remaining potato mixture to make 3 more stacks. Bake for 30 minutes or until golden. Place a potato stack on top of each dish with the beef. Bake for 15 mins at 200 degrees Celsius. Sprinkle with thyme sprigs.