Preheat oven to 425 F, and place your top oven rack 8" away from the bottom of your broiler. Place chicken on a plate and pat completely dry with paper towels.
In a small bowl, combine the butter, miso, honey, rice vinegar, sriracha, and ginger.
Heat vegetable or avocado oil in a large pan over high heat. Once oil is shimmering and the pan is hot, add the chicken skin side down and sear until the skin is crispy and no longer sticks to the pan. You may need to do this in batches depending on your pan size so you don't overcrowd the chicken. If your pan is oven safe, remove it from heat and place all chicken skin side up in the pan. If not, transfer chicken to a rimmed baking sheet.
Use a pastry brush to brush miso butter all over the top of each chicken thigh. Cover your pan with foil, and bake in preheated oven for 30-40 minutes, until the internal temp reaches 165 F. For slightly charred chicken, crank your oven to broil, and broil the thighs for another 1-3 minutes before removing. (NOTE: remove parchment paper before broiling, if you're using it)
Sprinkle chicken with sesame seeds and green onions before serving, and enjoy!