Take a pan,put a 2 tsp oil in it. Now add ginger,garlic, and onion

Saute it.....till it change it colour brown

Now add reshamchilly paste,salt,blackpepper,vinegar,
Red chilli sauce

Cook it 5 minutes....until it become sauce consistency

Now turn off flame and than add tomato ketchup

Your schezwan sauce is ready.....it is much healthier than readymade...because readymade sauce contains much vinegar

You can store this sauce upto 2 months in deep freezer