Cook the garlic and onion in the olive oil in a sauce pot over a medium-low flame, about 10 minutes or until garlic is tender and onions translucent, not brown (this is called"sweating" because it will draw out a lot of moisture and flavor).
Add the chili flakes to taste.
Add all the tomato products.
Pour the chicken stock into one of the 28-oz cans.
Fill it the rest of the way with water and add that and the sugar to the pot.
Stir and bring to a simmer.
Taste and season with salt and cover.
Simmer the sauce for about 1 hour (the sauce should be fairly thin, but not watery and very smooth).
Uncover and simmer for 3 minutes if it is too thin for your taste; add a little water if it seems thick.