Confusing - is this cooked in one pan or two? Can't pour chicken into the blender.

To add to what Nancy said, if you look at the photo, you can see that there are chunks of onions and carrots, which I think make the instructions even more confusing. Amanda (Food52 co-founder) has a recipe for braise-roast chicken. You could follow that process (https://food52.com/recipes/8192-spatchcocked-and-braise-roasted-chicken), but use the vegetables and aromatics in this recipe, and either roast everything in the oven, or braise it on the stovetop. If it were me and summer (which it is here in Austin, TX), I’d make the vegetables on the stovetop (and probably not bother blending it because who wants to clean a food processor in the summer? You could mince everything and it would just get saucy in the pan if that’s what you’re going for.), and grill the chicken (getting my husband involved, yay), and serve the grilled chicken with the vegetables/sauce on the side.

Yes, it's confusing. Also because the head note and the directions suggest two different ways to serve.
To make tomatillo sauce - remove everything but the chicken to the blender or processor. Blend.
At this stage you could either
1) pour the sauce back into the pan, warm everything and serve.
2) serve the chicken and sauce separately at table.
Implicitly, from the head note and the author favoring one-pot meals, you could even serve the whole thing a third way - without using and having to wash a blender or processor.
The softened vegetables, aromatics and liquid will provide a combination of sauce and side dish to the chicken (best served in a deep plate or soup bowl).