01 - Preheat oven to 400°F (200°C). Grease a large baking dish.
02 - Cook pasta in salted boiling water for 2 minutes less than package instructions. Drain and set aside.
03 - In a saucepan over medium heat, melt butter. Add chopped onion and sauté until translucent, about 5 minutes. Stir in minced garlic and cook for 1 minute.
04 - Stir in white miso paste and maple syrup. Cook for 1 minute until aromatic.
05 - Gradually whisk in whole milk, vegetable broth, soy sauce, and ground black pepper. Simmer, stirring occasionally, until slightly thickened, about 5 to 7 minutes.
06 - Remove saucepan from heat. Add grated Gruyère or cheddar and half of the Parmesan cheese, stirring until melted and smooth.
07 - Add drained pasta to the sauce and mix thoroughly to coat evenly. Transfer to prepared baking dish.
08 - In a small bowl, toss panko breadcrumbs with olive oil and remaining Parmesan cheese. Distribute topping evenly over pasta.
09 - Bake uncovered for 20 minutes, or until golden and bubbling.
10 - Let the baked pasta rest for 5 minutes before serving. Garnish with chopped parsley if desired.