Heat the oil in a heavy-based pan. Add the beef and brown all over, stirring regularly.
Add the mushrooms and pour over the water or beef stock. Bring the mixture to a simmer. Half-cover the pan with a lid and continue to cook the mixture over a high heat, stirring regularly, for 30-45 minutes, or until the volume of liquid has reduced, the sauce has thickened and the meat is tender enough to break down using a wooden spoon.
For the tomato salsa, in a bowl, mix together all of the tomato salsa ingredients until well combined.
Add the cooked, drained pasta, softened butter and half of the grated parmesan to the slow-cooked beef and mushrooms, stirring well until the pasta is coated in the sauce and the butter has melted.
Divide the pappardelle with slow-cooked beef and mushrooms equally among four serving bowls. Spoon over the tomato salsa and sprinkle over the remaining parmesan.