Season the chicken leg quarters generously with kosher salt. Combine the potato starch and baking soda in a fine mesh strainer and dust the leg quarters on each side with this mixture. Set aside for 30 minutes to crisp the skin.
Heat a grill for medium heat. Melt the butter in a medium saute pan over direct heat. Add the hot sauce and stir to combine well. Let this mixture hang out off heat while you grill chicken.
Make the blue cheese sauce by mixing together the sour cream, mayo, blue cheese, kosher salt and pepper. Chill while the chicken cooks.
Cook the chicken leg quarters over direct medium heat for 35 to 40 minutes, turning often, or until they reach 165 degrees F. When they reach this temp, use tongs to swath them through the buffalo sauce on both sides, even spooning over some of the sauce. Then return to the grill until they are caramelized and reach 170 degrees, and additional 10 to 15 minutes. Serve the leg quarters with a sprinkling of green onion and the blue cheese sauce.