4 large russet potatoes, peeled and cut into 3/4-inch cubes
1 tbsp. olive oil
3 tbsp. butter
1 lb. ground sirloin
1 lb. ground lamb
1 small onion, finely chopped
1 carrot, chopped
1 stalk celery, finely chopped
1 tbsp. Worcestershire sauce
2 tbsp. fresh thyme leaves, chopped
2 cloves garlic, chopped
1 tsp. ground caraway or whole caraway seeds
1 tsp. ground cumin
2 tbsp. flour
½ cup white wine or dry sherry
1 can (10.5 oz.) beef consommé or 1 1/2 cups beef or chicken stock
¾ cup sour cream
¼ cup fresh chives, chopped
1 large egg yolk
8 oz. shredded Gruyère or white cheddar
⅓ cup (a handful) fresh flatleaf parsley, finely chopped
In a medium pot, cover the potatoes with cold water. Bring to a boil over high heat. Salt the water and reduce heat a bit to keep the water at a gentle boil. Cook the potatoes until tender when pierced with a knife, about 15 minutes.
Meanwhile, heat a large castiron skillet over medium-high. Add the oil, one turn of the pan, then add 1 tbsp. butter. When the butter melts, add the ground meat; cook, stirring often and breaking up the meat with a spoon, until browned, about 8 minutes. Season the meat with salt and pepper. Add the onion, carrot, celery, Worcestershire, thyme, garlic, caraway, and cumin. Cook, stirring often, until the vegetables soften, about 8 minutes. Stir in the flour. Add the wine and consommé and stir until thickened, about a minute. Reduce heat enough to maintain a simmer.
Turn on the broiler.
Drain the potatoes. Using a potato ricer or food mill, puree the potatoes back into the hot pot. Mix in the remaining 2 tbsp. butter, the sour cream, chives, and egg yolk; season.
Spread the potatoes over the meat and veggies in the skillet. Top with the cheese. Broil until the top is browned and the edges bubble, about 4 minutes. Top with the parsley. Serve the pie directly from the skillet.