Preheat the oven to 400°F. Lightly grease a 9 × 13-inch baking dish.

Place the potatoes in a large pot and cover them with cold salted water. Bring to a boil and cook for 15–20 minutes, or until fork-tender.

While the potatoes cook, heat the olive oil in a large skillet over medium-high heat. Add the ground lamb and cook until browned, breaking it apart as it cooks. Drain off excess grease if needed.

Add the onion, carrots, and celery to the skillet. Cook for about 6 minutes, until the vegetables begin to soften.

Stir in the garlic and cook for about 30 seconds.

Add the tomato paste and Michelle’s Mexican Mocha Mix™. Stir well and cook for about 1 minute. This helps the cacao and spices blend into the savory filling.

Stir in the Worcestershire sauce, thyme, and rosemary.

Sprinkle the flour over the meat mixture and stir until everything is evenly coated. Cook for about 1 minute.

Slowly pour in the beef broth while stirring. Bring the mixture to a gentle simmer and cook for 8–10 minutes, until the gravy has thickened.

Stir in the peas and corn. Taste and season with salt and black pepper as needed.

Drain the cooked potatoes well. Return them to the hot pot for about a minute to allow excess moisture to evaporate.

Add the butter, warm milk, ½ cup cheddar, egg yolk, salt, and black pepper. Mash until creamy and smooth.

Spread the lamb mixture evenly in the prepared baking dish.

Spoon the mashed potatoes over the filling and spread them all the way to the edges. Use a fork to make ridges across the top.