For potatoes:
Heat 2 tablespoons olive oil in 4 quart saucepan over medium-high heat. Add lamb, salt, pepper, and thyme. Saute until all fat has rendered and meat is no longer pink.
Drain fat from meat using fine-mesh colander. If you like the taste of lamb, add ½ cup of the fat back to the pan (most of the flavor of lamb is in the fat). If you don’t like the taste of lamb, add a few tablespoons of olive oil or butter instead.
Add vegetables and parsley to the pot along withe ½ cup of water (or stout) and cover. Cook over low heat until vegetables are soft, about 10 minutes. If mixture has dried out, add some water to make a bit of sauce. Stir in and turn into 9” deep-dish pie plate.
Meanwhile, cover potato pieces with salted water. Boil until tender. Strain and turn back into pan. Add butter and mash with potato masher until no lumps remain and butter is melted. Stir in milk and cheese, then season to taste with salt and pepper. Spoon over filling in pie pan.
Preheat oven to 350 degrees with convection. Place pie plate on baking sheet and bake 30-40 minutes, until top is browning with crispy edges. Cool 10 minutes before serving.
