*The less brown the plantains are, the longer they will take to cook. If you have totally brown plantains (which are sweeter), you could also make them with cinnamon instead of garlic. These are delicious on their own! (But would probably be a little odd with chimichurri).
After cooking, yellow plantains don't keep very well as leftovers, and taste pretty weird after being stored in the fridge. So don't feel bad about eating them all :) Brown or (yellow with lots of brown spots) plantains DO keep well in the fridge, and taste delicious cold!
Chimichurri is also great on steak, eggs, chicken, pork, or just about any vegetable/salad. The sauce will keep for several days in the refrigerator.