1 onion, cut in half
1-2 carrots, cut into thirds
2 stalks of celery
kitchen scraps (mine already included fennel, parsley, green onions etc)
Fry up your onion, carrots and celery first with a small amount of olive oil.
Add all ingredients into a large pot with around 6 cups of water or enough to cover the scraps.
Bring to boil then cover and simmer for 1 hour, or longer if you like. I like leaving it to simmer for 2 hours or more if I have the time because the flavour is stronger.
Once liquid is cool enough store in freezer, I used zip lock bags in 2 cup lots.
Now I use 1/2 cup silicon molds or 1 -2 cup plastic food containers because my bags kept leaking.