This is the way my mother was told to make Chicken Adobo by her FILIPINO friend when I was child. I've spent my adult life perfecting my own recipe for this and every Filipino I've ever met makes it differently. They say there are no rules for making it. It's a very personalized dish to most Filipinos. I use equal parts RICE vinegar and soy sauce in mine but some people use NO vinegar. It's a fantastic dish that is easy to play with.
I agree with Chef#472116's comment about how this dish is a vinegar based recipe. 3 tbsps of vinegar to 1 cup of soy sauce is not an authentic ratio. Sorry to rate this so low because of that!
There should be more vinegar than soy sauce. adobo is a vinegar based recipe. it's popular because it preserves the meat. It is also NOT traditional to use onions. Try putting some sugar and 2 pieces of anise seeds.
Really tasty! I used skinless boneles breasts and cooked it in cooking spray. (I also halved the recipe, using 2.5 pounds of breasts.) I felt the other ingredients were right on for amounts. I served it over cooked pearl barley and we really enjoyed it, even the kids. My husband, who hasn't had adobo in about 12 years, said it was good. He couldn't remember if it tasted authentic, but he enjoyed it!