Before starting, preheat the broiler to high. Wash and dry all produce. Peel, then cut potatoes into 1/2-inch pieces. Add potatoes, 2 tsp salt and enough water to cover (by approx. 1 inch) to a large pot (use same for 4 ppl). Cover and bring to a boil over high heat. Once boiling, reduce heat to medium. Simmer uncovered, until fork-tender, 10-12 min.

Meanwhile, peel, then mince or grate garlic. Strip 1 tbsp (2 tbsp) thyme leaves from stems. Heat a large non-stick pan over medium-high heat. When hot, add 1/2 tbsp (1 tbsp) oil, then mirepoix, thyme and garlic. Cook, stirring occasionally, until veggies start to soften, 3-4 min. Season with salt and pepper.

Add lamb to the pan with veggies. Cook, breaking up lamb into smaller pieces, until no pink remains, 4-5 min.** Add peas, tomato sauce base, soy sauce and 3/4 cup (1 1/2 cups) water to the pan. Cook, stirring occasionally, until sauce thickens slightly, 5-6 min. Season with salt and pepper.Remove from heat and transfer lamb mixture to an 8x8-inch baking dish (9x13-inch for 4 ppl).

Drain and return potatoes to the same pot, off heat.Mash 2 tbsp (4 tbsp) butter into potatoes until creamy. Stir in sour cream. Season with salt and pepper.Top lamb mixture with mashed potatoes. Smooth mashed potatoes over top, covering lamb mixture.

Sprinkle Parmesan over assembled shepherd's pie. Broil in the middle of the oven until topping is golden-brown, 2-3 min. (TIP: Keep an eye on it so it doesn't burn!)

Let shepherd's pie cool slightly, 4-5 min. Divide shepherd's pie between plates.