Preheat the oven to 180C.
Using the medium edge of your grater, grate the sweet potato and combine it together with the onion, sage, capers and beaten egg. Heat an anodized pan with 1 tbs olive oil and spoon the mixture into individual patties (approx 8cm by 1cm thick)
Gently fry for 2 minutes before turning for a further 1 minute.
Transfer the rosti to a baking sheet lined with paper and cook in the oven for a further 10 minutes.
Slice kangaroo fillets to approximately 125g portions and using a meat mallet gently flatten the fillets out. Heat pan with oil, seal off kangaroo fillets on both sides, season with pepper and cook for 2 - 3 minutes each side. Cover and allow to rest for 5 minutes.
Blanch the cavalo nero in boiling water for 3 minutes. Drain. Heat a pan with 1 tbs olive oil. Gently sauté the garlic and add the cavolo nero. Saute for a further 3 - 5 minutes.
Serve the kangaroo fillets over the rosti with accompanying cavalo nero.
Note: Cavolo Nero grows in huge bunches in the gardens of most homes in Tuscany, hence its other name Tuscan kale. Unlike many other green veggies, cavolo nero holds it's shape when cooked. Like kale it's full of fabulous nutrients including antioxidants, vitamin K and beta carotene. Remove the stalks from the centre of each leaf and cut it into strips before cooking.