Preheat oven to 350°F.
Lightly coat a 2-quart baking dish with cooking spray.
Boil macaroni in lightly salted water for 7-8 mins until just done. Meanwhile, melt 3 tbsp margarine in a medium saucepan over medium hot.
Add flour and mustard and cook for two minutes.
Add warm soymilk, salt, onion powder, pepper, cayenne and nutmeg.
Cook, stirring often until mixture thickens and just comes to a boil, about 5 mins.
Remove from heat and stir in 1 cup of the cheese of your choice. Stir until it melts.
Add cooked macaroni and stir until evenly combined. Pour into prepared dish and sprinkle with remaining ½ cup of cheese.
Prepare topping by mixing 3 tbsp melted margarine with panko breadcrumbs until evenly coated and sprinkle over macaroni and cheese.
Bake in preheated oven for 30 mins. Serve warm.