01 -  Preheat oven to 400°F (200°C) and grease a medium baking dish. 
 02 -  Boil macaroni in a large pot of salted water according to package directions until al dente. Drain and set aside. 
 03 -  In a saucepan over medium heat, melt 2 tablespoons butter. Stir in flour and cook for 1 minute, forming a roux. 
 04 -  Gradually whisk whole milk into the roux, stirring constantly until thickened, about 3 to 5 minutes. 
 05 -  Add cheddar cheese, mozzarella, Japanese curry powder, curry paste, soy sauce, garlic powder, onion powder, salt, and pepper. Stir until cheese melts and sauce is smooth. 
 06 -  Add cooked macaroni to the cheese sauce and mix thoroughly. Transfer mixture to the prepared baking dish. 
 07 -  Melt 3 tablespoons butter in a skillet. Add panko breadcrumbs and toast over medium heat until golden. Stir in sesame seeds. 
 08 -  Sprinkle the toasted panko mixture evenly over macaroni and cheese. 
 09 -  Bake in preheated oven for 20 to 25 minutes, until bubbling and golden brown on top. 
 10 -  Top with sliced spring onions and pickled ginger before serving, if desired.