In a slow cooker, combine the evaporated milk, Dijon mustard and garlic powder.
Add the milk and macaroni. Season with salt and pepper and stir.
Mix together the shredded cheese and cornstarch, then sprinkle over the macaroni.
Cover and cook on high for 1 hour and 15 minutes. Stir occasionally to obtain a rich and creamy sauce. Let rest for 15 minutes and stir before serving.
Prepare the spiced breadcrumb mixture. In a frying pan over medium heat, melt the butter and sauté the garlic. Add the bread crumbs and nuts, then stir to ensure thorough browning. Add the spices and stir again. Remove from heat when the breadcrumbs have browned and the nuts have become crispy.
Serve the macaroni and cheese individually in bowls and garnish with the spiced breadcrumbs.