Season the Tomahawk steak generously with salt and pepper on both sides. Let it sit at room temperature for about 30 minutes before cooking.

In a large skillet over medium-high heat, add olive oil. Once hot, sear the Tomahawk steak for about 4-5 minutes on each side until a deep golden-brown crust forms. Remove the steak from the skillet and set aside.

In the same skillet, add the sliced leeks. Sauté for about 3-4 minutes until softened.

Pour in the balsamic vinegar and scrape the bottom of the skillet to release any browned bits. Bring to a simmer and cook for about 2-3 minutes until slightly thickened.

Return the Tomahawk steak to the skillet, nestling it among the leeks. Add the chopped marjoram and cover the skillet. Lower the heat to medium-low and let it braise for about 1 hour or until the steak reaches your desired doneness.

While the steak is braising, place the diced turnips in a pot of boiling salted water. Cook until tender, about 15-20 minutes. Drain and return to the pot.

Add heavy cream and unsalted butter to the cooked turnips. Using an immersion blender or a food processor, blend until smooth. Season with salt and pepper to taste.

Once the steak is done, let it rest for 10 minutes before slicing. Serve slices of the Tomahawk steak over a bed of smooth turnip purée, spooning the balsamic-glazed leeks on top. Garnish with fresh herbs if desired.