In a large stock pot, add tomatillos, onion, serrano chiles, garlic, and enough water to cover everything.
About 2 cups.
Cover and bring to a boil.
Continue to cook for 5 minutes.
Drain and let cool slightly.
Add the cooked tomatillos, onion, chiles, garlic, cumin, and 1 teaspoon salt to a blender.
Blend until smooth.
Set aside until ready to use.
Season the Rumba Meats beef hind shanks with salt and pepper on both sides.
Heat oil in a large skillet.
Add the beef hind shanks to the pan.
Sear the meat for 5 minutes.
Then turn and brown the other side.
Cook for an additional 5 minutes.
Add the salsa verde slowly.
Warning: It will splatter.
Cover the skillet and cook for 20 minutes.
Serve with rice and veggies.