Complex sentence: Other commonly used ingredients include tomatoes, onions and chilis added to the base; northern recipes use mashed potatoes in a spicy onion base, as almost no north Indian food can be made without potato.
Split into simpler sentences: Other commonly used ingredients include tomatoes, onions and chillies added to the base. Some also include mashed potatoes in a spicy onion base, as almost no north Indian food can be made without potato.