Preheat oven to 180°C (fan)/200°C/gas mark 6.
Place 15 muffin cases in a muffin tin.
Sift 125g plain flour, 125g wholemeal flour, 1 tsp baking powder, 1/2 tsp bicarbonate of soda, 1 tsp ground cinnamon, 1/2 tsp mixed spice and 1/4 tsp nutmeg together in a large mixing bowl. Stir in 125g sugar. Use your fingers to break down any lumps if needed. Stir in the 1/2 tsp salt if using.
In a separate bowl or jug whisk together 200g sweet potato purée, 120ml oat milk, 120ml sunflower oil, 1 tbsp cider vinegar or lemon juice and 2 tbsp maple syrup if using.
Fold the pumpkin mixture into the flour until just combined, stir in 100g raisins if using, then spoon into the muffin cases.
Bake in the centre of the oven for 25 minutes or until a skewer inserted in the centre comes out clean and the muffins are firm to the touch.
Allow to cool in the tin for five minutes then remove and allow to cool completely on a wire rack.
Store in an airtight container for 2-3 days or can be frozen.