Preheat oven to 350 degrees.

Steam potatoes until easily pierced with a fork. Set aside.

Meanwhile, heat 1 Tbsp of oil in a large, oven-safe skillet. Add carrots and onions and saute until onions are slightly translucent.

Add garlic and lamb, and saute until the meat is just brown.

Add peas, water, and tomato paste. Season to taste with salt and pepper. Reduce heat to low and simmer for 5 minutes.

Meanwhile, mash the potatoes, adding remaining olive oil, rosemary, and salt and pepper to taste. Mix evenly, adding more olive oil if necessary to achieve a creamy texture.

Spread meat mixture into a thick, even layer in skillet. Spoon potatoes over top, pressing gently into an even layer.

Cross-score with a fork and drizzle with olive oil.

Bake 20 minutes or until crust is golden.