Preheat the oven to 180C.
Cut the cabbage into 1.5 cm thick steaks. Rub them with the oil on both sides and place them on a baking tray. Slice the onion and scatter them around the cabbage.
Scatter the marjoram on top, then season with salt and pepper.
Bake in the oven for 10 minutes.
Meanwhile, mix the balsamic vinegar with the maple syrup or honey.
Take the tray out of the oven and carefully turn the cabbage steaks over and brush them generously with the balsamic mixture.
Put the tray back into the oven and roast for another 10 minutes or until the cabbage has caramelised lightly.
Scatter the chestnuts around the cabbage for the last 2 minutes of roasting.
Serve warm, garnished with fresh herbs of your choice.