01 - Preheat oven to 400°F. Grease a medium baking dish and set aside.
02 - Cook elbow macaroni in a large pot of salted boiling water per package directions until al dente. Drain thoroughly; set aside.
03 - In a saucepan over medium heat, melt 2 tablespoons butter. Sprinkle in flour and whisk constantly for 1 minute until mixture is smooth.
04 - Gradually pour in 2 cups whole milk, whisking continuously to prevent lumps. Simmer, stirring, until thickened, 3–5 minutes.
05 - Reduce heat to low and stir in shredded cheddar, mozzarella, Japanese curry powder, curry paste, soy sauce, garlic powder, onion powder, salt, and black pepper. Mix until cheeses melt and sauce is creamy.
06 - Fold cooked macaroni into cheese sauce until evenly coated. Transfer mixture to prepared baking dish.
07 - In a skillet, melt 3 tablespoons butter. Add panko and stir frequently until crumbs turn golden brown. Stir in sesame seeds for even distribution.
08 - Sprinkle toasted panko mixture evenly over the surface of the macaroni cheese.
09 - Bake uncovered for 20–25 minutes or until sauce is bubbling and the topping is crisp and golden.
10 - Finish with sliced spring onions and pickled ginger, if desired. Serve immediately.