Trim the fat cap off the bottom of the roast.
In a shallow sauté pan, heat 2 TBSP olive oil to the smoking point. Place the roast in the pan and brown on all sides . This should take about 5-7 minutes total. Set the roast aside.
In the same pan, add in 1 TBSP of olive oil and sauté 1/4 cup of chopped onion until softened.
To the pan, add in the tomato paste and cook in the sautéed onions for 1 minute on low heat. Add a splash of beef broth (1/4 cup) to loosen any browned bits from the pan. Pour the onion mixture into a slow cooker on low heat.
To the slow cooker add in the remaining beef broth, peppercorns, salt, smoked paprika, garlic cloves, rosemary, sage, bay leaves to the onion mixture. Whisk to combine all the ingredients.
Place the browned roast in the slow cooker with the sauce. Cover and cook on low for 6 hours. If possible, turn the roast once during cooking so that all sides are in the sauce.
After 6 hours, add the remaining chopped onion, carrots and potatoes to the cooker. Cook on low for an additional 1 1/2 hours or until the vegetables are fork tender, but not mushy. If desired, add a splash of cognac or red wine.
Remove and shred the beef with a fork into chunks or slice the beef against the grain to serve. Place the vegetables on a platter. Plate the beef among the vegetables. Pour the au jus into a gravy boat. Remove and discard the peppercorns u0026 rosemary stems.