Spread the diced beef out on a chopping board and tap each piece a couple of times with a rolling pin. Pile the flattened beef ribbons on top of each other and cut into strips. Mix the chopped beef with the chilli sauce, paprika and cumin seed. Finely dice the onions and fry in the oil over a low/medium heat for 10 minutes. Add the beef, garlic, squash and tomato purée and give it all a good stir. Put the lid on and cook for about 30 minutes until everything has begun to mulch together, stirring occasionally.