Preheat your grill or a cast-iron skillet over medium-high heat.

In a small bowl, mix together the cracked black pepper, sea salt, and dried thyme. Rub this spice mixture all over the Tomahawk steak, ensuring an even coating.

Drizzle olive oil on the grill or skillet. Once hot, place the Tomahawk steak on it and sear for 4-5 minutes on each side until a nice crust forms. Remove the steak from the heat and set aside.

In the same skillet, add the sliced onions and char them until they are caramelized, about 5-7 minutes. Stir occasionally to ensure even cooking.

Add the mulberries and cook for another 2-3 minutes until they start to burst. Pour in the balsamic vinegar and scrape up any browned bits from the bottom of the skillet.

Return the Tomahawk steak to the skillet, then add the beef broth. Bring to a simmer.

Cover the skillet and reduce the heat to low. Braise the steak for about 45 minutes to 1 hour, or until the meat is tender and cooked to your desired doneness.

While the steak is braising, prepare the sage jus. In a small saucepan, melt the butter over medium heat. Add the minced garlic and sage leaves, cooking until fragrant, about 2 minutes. Pour in any remaining beef broth and simmer for 5-10 minutes. Strain the jus to remove solids, if desired.

Once the steak is done, remove it from the skillet and let it rest for 10 minutes.

Slice the Tomahawk steak, serve it on a platter topped with the charred onions and mulberry-balsamic glaze. Drizzle the velvety sage jus over the top and garnish with fresh thyme sprigs.