1. Make topping: Preheat oven to 425ºF. Line 2 large baking sheets with parchment. Toss cauliflower, celery root and garlic cloves with 1 tbsp oil, salt and pepper. Spread on sheets and roast until vegetables are very tender, about 30 minutes, stirring halfway. Set aside to cool slightly.
2. Squeeze garlic out of peels and place in a food processor along with roasted vegetables, parsley and 2 tbsp oil. Purée until smooth, adding milk, 1 tbsp at a time, if needed to thin. Season with additional salt and pepper.
3. Reduce oven temperature to 375ºF. Place a large sheet of foil or a baking sheet on bottom rack of oven.
4. Make filling: In a large cast- iron skillet on medium, heat 1 tbsp oil. Add onion, carrots, celery and ¼ tsp salt and cook, stirring occasionally, until vegetables are tender, about 6 minutes. Add minced garlic and rosemary and sauté until fragrant, 1 minute. Transfer mixture to a large bowl.
5. Add 1 tbsp oil and lamb to skillet; season with remaining ¾ tsp salt and black pepper. Cook, stirring, until meat is cooked through and most of liquid has absorbed, 8 to 10 minutes. Sprinkle with flour and stir until coated. Add tomato paste, broth and reserved vegetables. Bring to boil; stir, reduce heat to low and simmer for 1 to 2 minutes, until thickened.
6. Spoon topping over filling in skillet and carefully spread using a small offset spatula. Drizzle with remaining 1 tbsp oil. Bake on center rack until topping is golden and filling bubbles around edges, 20 to 25 minutes. Let stand for 10 minutes before serving. (Alternatively, you can make these in individual portions. Spoon filling and topping into 6 8-oz ramekins and bake at 425ºF for 10 to 15 minutes.)
TAKE IT TO GO: Pack in an airtight container. Reheat in a toaster oven until heated through.
- Serving Size 1/6 of recipe
- Calories 513
- Carbohydrate Content 21 g
- Cholesterol Content 83 mg
- Fat Content 38 g
- Fiber Content 5 g
- Protein Content 24 g
- Saturated Fat Content 13 g
- Sodium Content 663 mg
- Sugar Content 7 g
- Monounsaturated Fat Content 19 g
- Polyunsaturated Fat Content 3 g