How do I recreate a restaurant's sauce if I know the ingredients but not the ratios?
First, ask if they cook any of the ingredients. 

It's likely that they are all raw. 

Next, I would probably start with a mix with an approximate base that has the same color as the original sauce ( e.g. 1:1:1 with one clove of garlic). 

Save some of it on the side to use again, then add some of each ingredient to your base. 2:1:1:1 / 1:2:1:1 / 1:1:2:1 etc. 

Then taste each one, and that should give you some idea of how to tweak it next.