Before you start, preheat oven to 220°C (or 200°C fan bake). Bring a large pot of water to the boil with a lid. Set aside a medium baking dish.
Pat chicken dry and cut in half. Toss with half of the spiced and season with a pinch of salt. Heat oil in a large fry-pan on medium-high heat. Cook chicken for about 3 minutes each side until golden brown, but not cooked through.
Carefully separate 6 cabbage leaves, ensuring they stay intact. Cook in pot of boiling water for 3 minutes, until they start to soften. Drain well and set aside.
Meanwhile, prep kūmara, potatoes and carrot. Toss in a large bowl with remaining spiced, a pinch of salt and oil.
Lay out cabbage leaves and divide chicken and vegetables evenly between them. Fold edges over and place seam side down in reserved baking dish. Pour over stock and cover with foil.
Bake for 60 minutes, until vegetables are tender and chicken is cooked through.
When hāngī has 20 minutes cook time remaining, bring a medium pot of salted water to the boil. When hāngī has 5 minutes cook time remaining, cook broccolini for 3 minutes, or until tender. Drain well.
Serve hāngī with broccolini and Béarnaise on the side.
TIP As you only use the outer leaves of the cabbage, you'll have a lot left over. Use the excess to make your next dinner. We love cabbage braised with butter, lemon and garlic, or you could even try your hand at making kimchi!