Place the potatoes in a large steamer basket over boiling water in a pot; cover and steam for 10 minutes on medium-high heat. Add the cauliflower to the basket; cover and steam for about 15 minutes, until the potatoes and cauliflower are tender when pierced with the tip of a knife.
1 1/2 pounds (unpeeled) Yukon Gold or creamery potatoes, cut into 2-inch pieces
1 small head cauliflower (1 to 1 1/2 pounds), cut into florets
2/3 cup low-fat milk (1 percent)
2 tablespoons unsalted butter
1 1/4 teaspoons kosher salt
1 pound lean ground lamb
2 teaspoons olive oil
1 large onion, chopped
8 ounces white button mushrooms, stemmed, cleaned and finely chopped
2 teaspoons chopped fresh thyme (may substitute 1 teaspoon dried)
2 tablespoons flour
1 cup no-salt-added beef broth
1/4 teaspoon freshly ground black pepper
1 cup frozen green peas
Preheat the oven to 375 degrees. Have a 9-by-13-inch baking dish or casserole at hand.
Remove the steamer basket and drain the pot; return the pot to the stove top (off the heat). Transfer the still-hot vegetables to the pot; use a potato masher to mash them to the consistency you prefer.
Combine the milk and butter in a microwave-safe measuring cup; microwave on LOW just until heated through and the butter has melted (do not boil). Stir into the mashed mixture, along with 3/4 teaspoon of the salt.
Meanwhile, cook the ground lamb in a large nonstick skillet over medium heat, stirring occasionally, until browned, about 5 minutes. Transfer the meat to a plate. Drain/wipe out any fat remaining in the skillet.
Heat the oil in the (same) skillet over medium heat. Add the onion, stirring to coat; cover and cook for about 8 minutes, until softened. Add the mushrooms and thyme; cook uncovered, stirring occasionally, until the mushrooms are soft and their released moisture has evaporated, about 8 minutes.
Return the ground lamb to the skillet. Sprinkle the flour over the skillet mixture; cook over medium heat, stirring, for 2 minutes, then pour in the broth and add the remaining 1/2 teaspoon of salt and the pepper, stirring to incorporate. Once the mixture is barely bubbling, use a spatula to dislodge any browned bits from the bottom of the pan, then stir in the peas. Remove from the heat.
Distribute the meat mixture evenly in the bottom of the baking dish or casserole, then spread the potato-cauliflower mash evenly over the meat-mushroom filling, making sure to cover it completely. Place the baking dish or casserole on a baking sheet (to catch any drips from bubbling filling); bake for 20 to 25 minutes or until the mixture is heated through and the top is lightly browned.
Makes 8 servings; about 12 cups
Per Serving: Calories 280; Total Fat 12g (Saturated Fat 5g); Cholesterol 45mg; Sodium: 115mg; Total Carbohydrates 28g; Dietary Fiber 5g; Protein 17g