Preheat oven to 425°F.
Cover the potatoes with cold water and cook on medium high heat until tender, about 15 minutes.
Place the chicken on a parchment lined sheet pan. Season the thighs with salt and pepper.
Use the ⅓ cup of parmesan and put a layer on top of the thighs. Place in the oven, bake for 25-30 minutes until golden brown and the chicken is cooked through.
When the potatoes are tender, carefully flatten them, drizzle with 2 tbsp oil and season with salt and pepper. Place on a parchment lined sheet pan and bake until golden brown, about 15 minutes.
While chicken and potatoes are finishing in the oven, mix together the garlic, parsley, basil, green onions, 2 tbsp parmesan and 1 cup olive oil. Adjust the seasoning and set aside.
Place the potatoes on a serving plate, drizzle with the herb sauce and serve with the parmesan chicken thighs.