Preheat oven to 170°C (150°fan-forced). Season and dust brisket with flour. Heat half the oil in a large ovenproof casserole dish over medium heat and cook brisket for 5 minutes each side. Remove and set aside.
Add remaining oil to the same dish and cook onions for 5 minutes. Add carrots and garlic and cook for another 2 to 3 minutes. Return brisket to dish, fatty side up and pour stock around beef.
Brush the hickory sauce evenly over the brisket. Cover the pot with a lid and transfer to the oven, cook for 1 ¼ hours. Remove from oven and brush brisket with extra sauce. Return and cook uncovered for a further 20-30 minutes or until tender. Remove and rest for 15 minutes before slicing across the grain.
Meanwhile, cook macaroni in a large pot of salted boiling water according to packet instructions.
In a large saucepan, melt butter and add remaining flour over medium heat, stirring constantly with a whisk, for 1 to 2 minutes. Gradually add the milk, stirring constantly, until smooth. Gently bring to the boil and remove from heat. Stir in mustard and green onions then add cheese and stir until melted. Season and add cooked pasta to the cheese sauce.
Serve brisket with braised vegetables, Mac ‘n’ cheese and broccolini.
You can use any kind of barbecue or tomato sauce for the brisket glaze.
Serve with creamy potato mash instead of mac’n cheese, if desired.