Step 1
Preheat the oven to 375 degrees F (190 degrees C).
Step 2
Place olive oil and butter in Dutch oven over medium heat. Stir in onion and ground lamb; brown the meat breaking it up into small crumbles as it cooks about 10 minutes.
Step 3
Stir in flour until incorporated then mix in salt black pepper rosemary paprika cinnamon ketchup and garlic; cook and stir until garlic is fragrant 2 to 3 minutes.
Step 4
Stir in water and scrape 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 about 5-6 minutes.
Step 5
Remove lamb mixture from heat and stir in peas and carrots until combined.
Step 6
Spread lamb mixture into the bottom of a 9x13-inch baking dish and set aside.
Step 7
Place potatoes into a large pan of salted water. Bring to a boil reduce heat to medium and cook until tender about 15 minutes. Drain well and return potatoes to pan.
Step 8
Mash butter cayenne pepper cream cheese and Irish cheese into the potatoes. Mash until combined and potatoes are smooth. Season to taste with salt and black pepper.
Step 9
Whisk together egg yolk and milk in a small bowl; stir into the mashed potato mixture.
Step 9
Top the lamb mixture in the baking dish with the mashed potatoes and spread evenly to cover.