To make mayo, combine mayonnaise, chili paste and mirin in large bowl; mix well to combine. Set aside.
Cook pasta to al dente; drain. Hold warm for service.
Heat Extra Melt Cheese Sauce and miso paste in large saucepan, stirring frequently. Gently stir in cooked pasta.
Brush bok choy with oil; grill, cut-side down, until tender.
To serve, drizzle Japanese Spicy Mayo over mac and cheese; garnish with half of bok choy and sprinkle of furikake.
To easily incorporate miso into cheese sauce, use a food processor before heating through.