Preheat the oven to 375°F (190°C).

In a skillet, melt 2 tablespoons of butter and sauté the onion, carrots, and potatoes until softened.

Stir in the shredded corned beef and shredded cabbage.

Sprinkle 2 tablespoons of flour over the mixture and stir to combine.

Gradually add the beef broth, stirring continuously until thickened.

Add Dijon mustard, thyme, black pepper, and salt to the mixture.

Prepare the crust by combining 2 cups of all-purpose flour, 1 teaspoon of salt, and 1 cup of chilled and cubed butter; mix until the mixture resembles coarse crumbs.

Add ice water slowly until the dough comes together; roll out to fit a pie dish.

Fill the pie dish with the corned beef and cabbage filling.

Cover with the top crust, seal the edges, and make slits for steam to escape.

Bake in the oven until the crust is golden brown, about 30 to 40 minutes.