Preheat the oven to 240°C/220°C Fan/Gas Mark 9.
Wash the sweet potatoes, halve them lengthways and then cut each again similarly into 3 long wedges.
Mix with 3 tablespoons of the olive oil, 2 teaspoons of salt and some black pepper. Spread the wedges out on a baking sheet, skin-side down, and cook for about 25 minutes until soft but not mushy. Remove from the oven and leave to cool down.
To make a balsamic reduction, place the balsamic vinegar and sugar in a small saucepan. Bring to a boil then reduce the heat and simmer for 2-4 minutes, or until it thickens. Be sure to remove the pan from the heat when the vinegar is still runnier than honey; it will continue to thicken as it cools. Stir in a drop of water before serving if it does become too thick to drizzle.
Arrange the sweet potatoes on a serving platter.
Heat the remaining oil in a medium saucepan and add the spring onions and chilli. Fry on a medium heat for 4-5 minutes, stirring often, making sure not to burn the chilli, and then spoon the oil, onions and chilli over the sweet potatoes.
Dot the figs among the wedges and then drizzle over the balsamic reduction.
Serve at room temperature with the cheese crumbled over, if using.