Halve and peel red onion. Slice halves into ½" strips. Trim and thinly slice green onions on an angle, keeping white and green portions separate. Rinse pork, pat dry, and season both sides with ½ tsp. salt and ¼ tsp. pepper.
Make the Char Siu Glaze
In a small bowl, combine hoisin, light brown sugar, soy sauce, and 1 Tbsp. water. Stir until well-combined. Set aside.
Sear the Pork
Heat 1 tsp. olive oil in a medium non-stick pan over medium-high heat. Add pork to hot pan and cook until well-browned, 4-5 minutes per side. Transfer to a plate and reserve pan; no need to wipe clean. Pork will finish cooking in a later step.
Cook the Peppers
Heat a large non-stick pan over medium-high heat. Add shishito peppers to dry pan and stir often until blistered, 3-5 minutes. Remove from pan and return pan to heat with 1 tsp. olive oil. Add red onion, white portions of green onion, and snap peas to hot pan. Cook, stirring often, until slightly caramelized, 3-4 minutes. Add shishito peppers, 1 tsp. char siu glaze, and 2 tsp. water. Cook, stirring constantly, until liquid has evaporated and vegetables are tender, 2-3 minutes. Season with a pinch of salt and pepper.
Finish the Pork
Return pan used to sear pork to medium-high heat. Add remaining char siu glaze and pork chops and any accumulated juices to hot pan. Bring to a simmer and cook, flipping pork several times, until chops are glazed and reach a minimum internal temperature of 145 degrees, 4-5 minutes.
Plate the Dish
Serve vegetables on a plate along with pork. Garnish with remaining green onions.