Preheat the oven to 350°F/180°C.
Cook macaroni according to package directions in salted water, drain.
Meanwhile, in a saucepan melt the butter and add the flour, cook while stirring for 1-2 minutes. Add the seasonings: onion, garlic, and mustard powder. Stir until combined.
Gradually add in the milk while whisking constantly. Bring to a boil, then reduce the heat to low and simmer for 2 minutes.
Stir in the velveeta cheese, cook and stir until it’s melted. Remove from heat.
Stir in the shredded cheddar until it’s melted.
Stir in the cooked macaroni.
Transfer the cheesy macaroni to a casserole dish.
In a small bowl, combine the breadcrumbs and the butter and sprinkle them over the macaroni. Sprinkle with cheddar cheese, bake for 20 minutes or until golden.
Garnish with finely chopped parsley and serve.