Sprinkle the chicken thighs on all sides with salt and pepper. Place in a large bowl or baking dish, pour beer over chicken. Refrigerate for 30 minutes and up to 4 hours.
In a high powdered blender or food processer add the peas, garlic, sour cream, brown ale, salt, pepper, parmesan and olive oil, process until smooth.
Add the peas to a pot over medium low heat, simmer until warmed through, remove from heat.
Remove chicken from the brine, pat dry.
Place the chicken skin side down in a cold cast iron skillet, add the pan to medium high heat. As the pan heats, fat will render making the skin crispy. Once the skin is golden brown, turn the chicken thighs and cook until internal temperature reaches 165.
Plate the peas puree, add the chicken, sprinkle with green onions.