Corned Beef & Cabbage Shepherd's Pie Mashup

Corned beef and cabbage Shepherd's Pie mashup
featuring chef, Hugh Groman of Hugh Groman Catering 

12oz cooked corn beef, cut into cubes
12oz  savoy cabbage, blanched in salted water 3 minutes
8oz carrots, large dice, blanched in salted water until al dente
1/2  yellow onion, sliced and sauteed
1 Tablespoon butter
2 Tablespoons flour
1.5 cups  beef gravy 
2T  Dijon mustard, added to gravy
1 T  chopped parsley, chopped
1 teaspoon chopped fresh thyme
Salt and pepper to taste

For mashed potato topping:
1.5 lb  russet potatoes, boiled in salted water until just tender
1/2 cup whole milk, or to taste
4 Tablespoons butter, or to taste
salt and pepper

Cook potatoes and mashe with butter and milk.  Add salt and pepper to taste.  Add more milk as needed to get a soft consistency.
To make gravy:
Sautee onion in 1 T butter. Add 1 Tablespoon butter and 2 Tablespoons flour and cook a few more minutes to cook out flour.  Wisk in the beef stock and simmer a few minutes until thickened.  Add mustard.

In a large bowl, combine corned beef, blanched carrots and cabbage, gravy, fresh parsley and thyme. Mix well and pour into baking dish.  Pipe mashed potatoes on top in a decorative pattern.  

To serve:  Heat casserole in 400 degree oven for 20 minutes until very hot.