Navarin of Lamb Shepherd's Pie

Preheat oven to 325°F (160°C).

In a large Dutch oven or pot, heat olive oil over medium-high heat. Season lamb cubes with salt and pepper. Sear the lamb in batches until browned on all sides. Remove lamb from the pot and set aside.

Add onion, carrots, and celery to the pot and cook until softened, about 5-7 minutes. Add garlic and tomato paste, and cook for another minute, stirring constantly.

Deglaze the pot with red wine, scraping up any browned bits from the bottom. Cook until the wine is reduced by half, about 3-5 minutes.

Return the lamb to the pot. Add lamb broth, rosemary, thyme, and bay leaf. Bring to a simmer, then cover and transfer to the preheated oven.

Braise in the oven for 1 hour and 30 minutes, or until the lamb is very tender.

While the lamb is braising, prepare the mashed potatoes. Peel and quarter the russet potatoes. Place them in a large pot of cold, salted water and bring to a boil. Cook until tender, about 15-20 minutes.

Drain the potatoes and return them to the pot. Add butter, warmed milk, and heavy cream (if using). Mash until smooth and creamy. Season with salt and pepper to taste.

Remove the lamb from the oven. Stir in pearl onions, new potatoes, and turnip. Return to the oven and cook for another 30 minutes, or until the vegetables are tender.

Remove from oven and stir in the frozen peas.

Remove the bay leaf, rosemary and thyme sprigs from the lamb mixture. Taste and adjust seasoning as needed. If the gravy is too thin, simmer on the stovetop over medium heat to reduce to desired consistency.

Transfer the lamb mixture to a 9x13 inch baking dish.

Spread the mashed potatoes evenly over the lamb filling, creating swirls or peaks with a fork for a decorative touch.

Bake in the preheated oven at 375°F (190°C) for 20-25 minutes, or until the mashed potatoes are golden brown on top.

Let stand for 10 minutes before serving. Garnish with fresh parsley.