Submerge corned beef into a pot of cold water and cook on high to bring to a boil. Once boiling, lower to a simmer. Cook for three hours, flipping every 30 minutes. Peel carrots and cut on the bias.
Place angel hair slaw in the microwave in a heat-safe bowl with water, cover with plastic wrap and cook for one minute. Rinse with cold water, drain and set aside. Combine the cooked cabbage with the mashed potatoes and black pepper.
In a large, nonstick sauté pan, heat half of the butter on medium-low. Once melted, place the mashed potato-cabbage mixture into the pan firmly packing it down with a spatula so it resembles a large cake. Every minute or so, continue to press the cake down with the spatula. After 10 minutes, place large plate over the pan and flip cake onto pan. Melt the remaining butter and carefully place the potato cake back into the pan, unseared-side down, repeat the same process and set aside for serving.
Once corned beef is tender, very carefully remove from the pan (reserve cooking liquid) and place on a baking sheet. Heat oven to 425°F. Spread corned beef with the whole grain mustard in a thin layer and sprinkle brown sugar on top. Place in oven for 10 minutes or until a nice crust forms. Ensure that corned beef has reached a minimum internal temperature of 145°F before serving.
Meanwhile, bring the corned beef cooking liquid to a boil if it’s not already boiling. Submerge carrots and cook for 3 minutes. Remove and set aside.
Slice corned beef against the grain with a sharp knife and serve on top of a wedge of the potato cake and a helping of carrots.
Approximate Nutritional Information (Per serving):
Calories 600, Fat 28g, Sat. Fat 12g, Trans Fat 0g, Cholesterol 165mg, Sodium 2300mg, Total Carbohydrate 31g, Fiber 3g, Sugars 10g, Protein 29g
ALLERGEN INFORMATION: Tree Nut-Free, Peanut-Free, Egg-Free