Peel and cut the potatoes and boil until fork tender, about 10 minutes. Drain from the water and mash. Add the yogurt, butter, salt and garlic powder.
In a large skillet (or oven safe pot, depending on what you’re serving in), heat the oil over medium heat. Add shallots and sauté until fragrant. Add mushrooms, carrots and minced herbs and stir. Sauté until carrots soften.
Add the tomato paste to the skillet and stir. Add the red wine and let it cook out for a minute or two. Add the broth and stir.
In a small bowl, temper the arrowroot powder with a bit of the warmed liquid from the skillet. Mix until combined and pour into the skillet to thicken. Simmer over low heat until thickened.
Stir in the peas and season with salt and pepper.
If you’re making one large shepherd’s pie, spread the mashed potatoes on top. If you’re making smaller ones like I did, transfer the veggie mixture to the individual bowls and spread the mashed potatoes on top. Brush with additional olive oil and bake for 15 minutes at 350F. Finish with a few minutes on broil for golden brown edges.