Pre-heat the oven to 180°C (fan)/200°C/gas mark 6.
Grease and line a 900g loaf tin with baking paper.
Mix the flour, baking powder and cinnamon together in a mixing bowl.
Drain the dates and purée with 2 tsp water in a small food processor (if you use a large one it might not work as it's such a small quantity). If you use particularly sticky dates like medjool you won't need to soak or add water.
Add the sweet potato to the dates and pulse until puréed.
Pour the sweet potato and date mixture into the flour along with the oil and mashed banana. Mix well.
Stir in the flaxseeds, raisins and chocolate chips if using.
Transfer to the prepared loaf tin and smooth the top.
Bake in the oven for 30 minutes or until firm to the touch and a skewer inserted in the centre comes out clean.
Cool on a wire rack.