For the chilli: Heat the oil in a large frying pan and brown the beef in batches, along with the salt. Return all of the beef to the pan and add in the minced garlic. Cook for 1 minute then add in the cumin, chilli powder, oregano and cayenne chilli. Stir to combine then add in the passata. Cook for 20 minutes until the meat is cooked and you have a loose chilli. Add water if needed to make a thin chilli that you can ladle over the chips.
For the chilli fries: Line an oven tray with baking paper and lay out the oven fries on top. Cook according to the packet instructions, turning once or twice to get them evenly golden brown. Once cooked to your liking, sprinkle the grated cheese on top and gently toss to combine. Put the tray back into the hot oven until the cheese is melted. Top the hot tray of fries with warm chilli, drizzle with sour cream, and sprinkle with sliced spring onions to serve.