Husk the tomatillos and then rinse both the tomatoes and tomatillos. I usually remove the stems from both of them knowing that any juices leftover in the roasting pan will go into the blender.
Roast the tomatoes and tomatillos in a 400F oven for 20-25 minutes. Here's why roasting tomatillos is better than boiling them.
Add the roasted tomatoes and tomatillos to a blender along with ⅓ small onion, 1 peeled garlic clove, 1 rinsed and de-stemmed jalapeno (or less for a milder version), 10-12 sprigs rinsed cilantro. Combine well (I usually leave it a bit chunky.)
Take a taste for seasoning. I added another ½ jalapeno, a pinch of salt, and a generous squeeze of lime.
Serve immediately or chill in the fridge for a bit before serving.
Store leftovers in an airtight container in the fridge where they will keep for a few days.