Heat an oven to 400*F and arrange the tomatillos, sliced side down, on a sheet pan.
Roast the tomatillos until they have softened and have begun to brown, then transfer to a blender or food processor.
Add the lime juice, cilantro, garlic, and jalapeno if using and blend until smooth.
Turn the oven down to 350*F.
Season the chicken liberally on all sides with salt and pepper.
Line half the chicken at the bottom of an 8x8” casserole dish, then spread half the cheese on top.
Layer the other half of the seasoned chicken on top.
Pour the salsa verde into the chicken, gently pressing the chicken into it.
Top with remaining cheese and bake at 350*F for 20-30 minutes or until the cheese has melted and the chicken is cooked through.