• Start by cooking the potatoes: Place potatoes in a pot and cover with cold water. Set over high heat, and once the water is boiling, salt it generously. Cook until the potatoes are fork-tender, 10 to 12 minutes. Drain, and return the potatoes to the pot. Let them stand, covered, as you make the filling.

Filling:

• Set a wide skillet over medium-high heat, and once it’s hot swirl in the 1 tbs oil. Add the beef and salt, and cook until the meat is no longer pink, breaking it up with a spatula into crumbles. Use a slotted spoon to move the beef to a large plate, and drain off any fat in the pan.
• Return the pan to medium heat and swirl in a bit more oil if the pan is dry. Add the onion, carrots, and Italian seasoning. Cook until the vegetables are mostly tender, 5-6 minutes, stirring often. Add the cooked ground beef back in and then stir in the tomato paste, garlic, and Worcestershire, stirring constantly for 1 minute, until the garlic is fragrant. Sprinkle on the arrowroot powder and stir to coat all. Pour in the broth and bring to a simmer and cook for a few minutes. Remove from the heat and stir in the peas.
• Scrape the mixture into a 9- by 13-inch baking dish and spread it in an even layer.
• Preheat your oven to 400℉.

Topping:

• Use a masher or hand mixer to mash the potatoes, then stir or beat in the Parmesan, yogurt, milk, olive oil, and ½ teaspoon salt, until smooth and evenly combined.
• Dollop the potatoes over the meat filling and smooth it with a spoon or offset spatula to cover the surface. Garnish with a little more parmesan.
• Bake for 25 to 30 minutes, until the juices are bubbling at the edges and the topping is very lightly browned.
• Switch your oven to its broil setting, and place the pan beneath the heat source. Broil for 2 to 4 minutes, watching carefully, until the topping is lightly blistered.
• Cool for at least 15 minutes before slicing and serving. Garnish with chives or parsley.