Chop the onion and garlic. In a large bowl, add all other ingredients and whisk together. Set aside.
Heat the oil in saucepan over medium heat.
Add the onion and cook for about 5 minutes or so, until they soften and get a bit of color.
Add the garlic and cook it for about 30 seconds or so, just until fragrant but be careful not to burn it.
Add everything else in, (it'll spit – it's hot). Stir together, and bring to boil. Once it's boiling, turn heat down to about medium or so, to simmer. Simmer until it thickens up, about 20-30 minutes or so. Then it's ready to use.