Melt the butter in a medium saucepan over medium heat
Stir the onions and garlic around a lot in the pan while you cook them until they become clear and soft
Stir the sauce ingredients together until the sauce just begins to boil
Cook the sauce at medium-low heat for 20 to 25 minutes
Let the sauce cool down until it's barely warm
If you like the taste of onion and garlic in it, you can use it directly
To make the sauce smooth, place it in a blender, make sure the lid is tight, and mix on high speed until smooth
It is best to leave this sauce to sit overnight (24 hours is best for flavor)