Preheat oven to 190°C. Season the beef with salt and pepper, then wrap in sage and prosciutto. Tie securely with lengths of kitchen string. Drizzle with 2 Tbsp extra virgin olive oil, then arrange on a rack over a roasting pan. Bake for 1 hour, until the beef is 62°C when tested with a probe thermometer. Rest for 10 minutes.
Meanwhile, toss the kale with 1 Tbsp extra virgin olive oil, arrange on a lined oven tray, season with salt, then bake for 30 minutes, until crisp. Combine the polenta, stock and milk in a medium saucepan and bring gently to a simmer for 10 minutes.
Sauté the eschalots, garlic and rosemary in the remaining oil, then add the tomatoes, zest and marjoram. Cook for 5 minutes, until softened. Season with salt and pepper. Carve the beef and serve with polenta, kale chips and tomatoes.