Pre-heat the oven to 425 degrees. Line a baking sheet with parchment paper or aluminum foil.

Brush the cut sides of the sweet potatoes with 1 teaspoon of olive oil and place them cut-side down on the prepared baking sheet. Roast for 25 minutes or until very tender when pierced with the tip of a sharp knife. Let cool slightly. When the potatoes are cool enough to handle, remove their skins. (They should peel right off.) Transfer the flesh to a medium bowl, and add a teaspoon of olive oil, ¼ teaspoon cinnamon, and ¼ teaspoon kosher salt, and mash with a fork until very smooth. Set aside.

Reduce the oven temperature to 375 degrees.

Meanwhile, heat the remaining 1 tablespoon oil in a large skillet over medium heat. When the oil is hot and shimmering, add the cauliflower, carrots, and onion and cook for 5 to 6 minutes, until the cauliflower and carrots have softened slightly and the onion is translucent. Add the garlic, curry powder, chili powder; the remaining ¼ teaspoon cinnamon; the cumin, ginger, cayenne; and the remaining 1 teaspoon salt. Cook for 1 minute more to toast the spices. Add the lamb and cook for about 4 minutes, breaking up the meat with a spatula, until no longer pink. Stir in the chicken broth and simmer for 5 minutes, or until most of the liquid has been absorbed. Turn off the heat and stir in the peas and lemon juice.

Transfer the filling to a medium baking dish (a 9x9-inch or a 7x 11-inch dish is ideal) and top with the sweet potato mash, spreading it out in an even layer. Add a couple of dashes of chili powder if you like.

Bake the casserole for 20 minutes, or until piping hot and bubbling around the sides. Remove from the oven and let cool for 5 to 10 minutes. Serve garnished with fresh cilantro if you’re into that.