Preheat the oven to 400°F / 200°C and line a 12-hole muffin tin with muffin cases.
Peel and deseed the butternut squash, then chop into small cubes. Steam or microwave them until soft, then puree. You will need 1 cup/250g puree. The rest can be saved for another recipe. Allow it to cool slightly.
Whisk the flour, baking powder, cinnamon, ginger and both sugars together in a large mixing bowl.
Whisk the butternut squash purée and eggs together in a jug, then add to the dry ingredients with the melted butter. Beat for a minute or so to combine, then gently fold in the chocolate chips.
Spoon the mixture into the prepared muffin tray ¾ full and bake for 15 mins until golden and risen and a skewer or toothpick inserted comes out clean.
Place the muffins onto a wire rack to cool completely.
The butternut squash muffins will keep for 4 days in an airtight container.