Cut potato into twelve wedges. Place on prepared baking sheet and toss to coat with 1 Tbsp. olive oil, miso, ¼ tsp. salt, and ¼ tsp. pepper. Spread into a single layer and roast until tender and browned, 15-18 minutes, flipping once halfway through. While potatoes roast, prepare ingredients.
Prepare the Ingredients
Trim and very thinly slice green onions on a sharp angle. Mince garlic. Mince pineapple chunks. Pat chicken thighs dry, and season both sides with a pinch of salt and ¼ tsp. pepper.
Cook the Chicken
Place a medium non-stick pan over medium-high heat. Add 2 tsp. olive oil and chicken to hot pan. Cook until browned, 3-4 minutes per side. Transfer chicken to a mixing bowl and cover at least 5 minutes. Reserve pan; no need to wipe clean.
Make the Sauce
Return pan used to sear chicken to medium-high heat. Add pineapple juice, garlic, ginger, and soy sauce to hot pan. Bring to a boil and keep boiling until liquid reduces to a consistency that clings to the back of a spoon, 5-7 minutes.
Finish the Chicken
Shred chicken and return chicken and accumulated juices to pan with sauce. Stir in pineapple and bring to a boil. Remove from burner. Place buns directly on oven rack until lightly toasted, 2-4 minutes.
Finish the Dish
Place chicken on bottom bun. Top with green onions to taste and top bun.