There is something special about serving things quite simply, letting the individual flavours and ingredients stand up for themselves. The creamy beans in their broth help tie everything together. I often cook a big batch ahead of time to eat in different meals during the week. They are better for it and it makes this dish quick to pull to-gether. Using jarred or canned is fine if you are pushed for time, the method here brings them up to speed.
Based on 4 servings, adjust as needed.
Preheat the oven to 220°C (425°F), Gas Mark 7. Wash the sweet potatoes, cut into 2.5cm- (1-inch) thick slices, lay on a couple of baking trays and coat with around 4 tablespoons of neutral oil (if cooking for 4) and a sprinkle of salt. Roast in the oven for 20 minutes, then turn them over and roast for a further 15 minutes, or until golden on each side and giving to the touch.
Heat the olive oil in a pan, add the onion and garlic and gently soften over medium heat for 12-15 minutes. Add the rosemary, sage stalks, then the beans with their liquid. Heat through for 2 minutes, turn off the heat and set aside to infuse. (Don't forget to turn your sweet potatoes that are in the oven at this point).
Meanwhile, heat the remaining neutral oil in a frying pan over a medium heat. In batches, carefully add the sage leaves in a single layer; you don't want to overcrowd them. Cook for 2 minutes, turning once, until they stop bubbling, which means the moisture has evaporated. Remove and drain on some kitchen paper, not too clustered together, to soak up any excess oil and help crisp them.
To serve, spoon the beans onto a platter or individual plates. Top with the sweet potato and the sage leaves. Toss the red cabbage, taste a bit to check the seasoning and adjust accordingly. Serve the sweet potato on top of the beans and drizzle with olive oil. Top with a little drained pickled red cabbage.