Rinse and trim Brussels sprouts and place in microwavable container. Cover with plastic wrap and cook on high 3 minutes. Set aside.
Roughly chop 1/2 Vidalia onion. Melt 1 tablespoon butter over medium heat and add red pepper flakes. Cook 1 minute. Add onion and a pinch of salt. Cook until onions are softened and translucent, 6-8 minutes. Add Brussels sprouts and 1 tablespoon butter and increase heat to medium/high. Continue cooking until Brussels sprouts are golden and caramelized. Remove from heat and set aside.
Cook pasta in pot of salted boiling water to al dente.
Finely dice remaining 1/2 Vidalia onion. Sauté in 1 tablespoon butter over medium-high heat 5-6 minutes until softened. Add dried cranberries and remaining 1 tablespoon butter. Cook, stirring well, 1-2 minutes. Add 1 tablespoon flour and stir well to incorporate. Cook 2 minutes. Slowly add heavy cream and bring to simmer. Cook until sauce has thickened and coats back of spoon. Reduce heat to low and add cheese, stirring well. Stir in Dijon mustard and adjust salt and pepper to taste.
In large bowl, combine Brussels sprouts, pasta and cheese. Serve.