Irish Shepherd's Pie

Step 1
Preheat the oven to 375 degrees F (190 degrees C).

Step 2
Place olive oil and butter in a Dutch oven over medium heat. Stir in ground lamb and onion; cook and stir until meat is brown and crumbly, about 10 minutes.

Step 3
Stir in flour until incorporated. Mix in garlic, ketchup, rosemary, paprika, cinnamon, salt, and pepper; cook and stir until garlic is fragrant, 2 to 3 minutes.

Step 4
Stir in water, scraping up any brown bits from the bottom of the Dutch oven. Reduce heat to medium-low and bring mixture to a simmer; cook and stir until thick, 5 to 6 minutes.

Step 5
Remove lamb mixture from heat, then stir in peas and carrots until combined.

Step 6
Spread lamb mixture into the bottom of a 9×13-inch baking dish; set aside.

Step 7
Place potatoes into a large pot of salted water. Bring to a boil, reduce heat to medium, and cook until tender, about 15 minutes. Drain well and return potatoes to the pot.

Step 8
Mash Irish cheese, cream cheese, butter, and cayenne pepper into potatoes until smooth. Season with salt and black pepper.

Step 9
Whisk together egg yolk and milk in a small bowl; stir into mashed potato mixture.

Step 10
Top lamb mixture in the baking dish with mashed potatoes; spread evenly to cover.

Step 11
Bake in the preheated oven until the top is golden brown and sauce is bubbling up around the edges, 25 to 30 minutes.