Several months ago I wrote a post on food combining, which was about pairing certain foods together for better digestion, like having twice as much starch on your plate than protein. Protein complementation is about combining 2 sources of protein together to ensure you get the 9 essential amino acids.
There is a myth about plant-based diets and this protein complentation. It has been around for years, and like the question "where do you get your protein from?" It doesn't seem to go away.
Whole plant-based food has all of the essential amino acids, although they may not be complete. Take a baked potato, besides the having protein and the essential amino acids, it has 9 additional amino acids. Broccoli does too! And that's without pairing them together or with any other food.
I could eat nothing but 1 baked potato for lunch, and still get all those essential and nonessential amino aids. It doesn't need to be combined with any other food. Obviously if I eat something else I am increasing my intake of amino acids and protein, but there is no need to worry about what I am pairing together for my meals.
One of my favorite quotes from T. Colin Campbell in Forks over Knives is "You can’t be protein deficient unless you are calorie deficient." The same is true about essential amino acids.
Jeff Novick wrote an article last year saying if you are calorie sufficient it is 'virtually impossible' to be deficient in amino acids.
As long as you are eating a variety of healthy plant-based foods, you will not only get enough protein, but enough essential amino acids as well, with no worries about having to pair or complement certain foods together.
If you are wondering about the essential amino acid levels of your food, The World's Healthiest Foods is a great resource for the nutritional information of food and much more.