Lee’s sweet and sour sauce (this makes a huge amount, but can be batch frozen)

Ingredients:
2 thumb sized pieces of ginger with skins on.
2 lemons thickly sliced
1 large onion roughly chopped
1 whole bulb of garlic crushed with skin on
630 ml of vinegar (you can use malt or cider vinegar)
1 1/2 tubes of tomato puree
about 1 lb of sugar
approximately 1/2 pint of vegetable oil (enough to cover to almost cover the ginger, onions, garlic and lemon
2 teaspoons of cornflour
To finish off a sweet and sour dish you will need the following ingredients for 4 people:
1 1/2 peppers of mixed colours cut into large squares
1 medium onion
1 medium tin of pineapple chunks on juice
If you want, you can add the pineapple juice to the sauce
Optional Extras:
This is best served with the chicken balls (see the separate recipe).
Here’s what you do:
Step 1 - Fry the onion, ginger, garlic and lemon in the oil on a moderate heat for 10-15 minutes until it is very dark brown and starting to caramalise (do not allow to burn).
Step 2 - Drain through a sieve into a saucepan and then wash through with 1/2 pint of boiling water and squash the ingredients to extract as much juice as you can.
Step 3 - Add the vinegar and pineapple juice (if using) and bring to a rolling boil.
Step 4 - Whisk in the tomato puree, then thicken with cornflour to make the sauce the consistency of custard.
Step 5 - Start adding the sugar gradually. Keep on tasting the sauce and add the sugar to taste.
Kitchen implements required:
Chopping board
Sharp knife
Frying pan
Saucepan
Whisk