Classic Irish Shepherd's Pie with Creamy Potato Topping

1.Prepare the Mashed Potatoes: Place the peeled and quartered potatoes in a large pot and cover with cold, salted water. Bring to a boil and cook for 15-20 minutes, or until fork-tender. Drain well and return the potatoes to the hot pot to dry out for 1 minute over low heat.

2.Mash the potatoes thoroughly. Add the warm milk and butter, mixing until smooth and creamy. Season generously with salt and white pepper. Set aside.

3.Preheat oven to 200°C (400°F). Lightly grease a 9x13 inch baking dish.

4.Prepare the Filling: Heat the olive oil in a large, deep skillet or Dutch oven over medium heat. Add the onion, carrots, and celery. Sauté for 8-10 minutes until the vegetables begin to soften.

5.Add the ground beef to the skillet. Break it up with a spoon and cook until browned, about 5-7 minutes. Drain off any excess fat.

6.Stir in the minced garlic, tomato paste, thyme, and rosemary. Cook for 1 minute until fragrant.

7.Sprinkle the flour over the meat mixture and stir constantly for 1 minute to cook out the raw flour taste.

8.Slowly pour in the red wine (if using) and scrape up any browned bits from the bottom of the pan. Let it simmer for 2 minutes. Then, gradually stir in the beef broth and Worcestershire sauce. Bring the mixture to a simmer, stirring until the sauce thickens slightly.

9.Reduce heat to low, cover, and simmer for 10 minutes to allow flavors to meld. Stir in the frozen peas, season with salt and pepper to taste, and remove from heat.

10.Assemble the Pie: Pour the meat filling evenly into the prepared baking dish.

11.Carefully spoon the mashed potatoes over the filling. Use a fork or spatula to spread the potatoes evenly across the top, making sure to seal the edges. Create decorative peaks or ridges with the tines of a fork—this will help them brown nicely.

12.If using, sprinkle the grated cheddar cheese evenly over the potato topping. Lightly brush the surface with the beaten egg yolk for extra color.

13.Bake for 25-30 minutes, or until the filling is bubbling around the edges and the potato topping is golden brown and crisp. Let the pie rest for 10 minutes before serving.