Reader request: "Royal shepherd's pie." —Heidi James Plotkin, Malibu, California
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.