You can swap the blueberries to any filling that you want. Let me know how you get on and what you think too the recipe:

Here's a simple blueberry muffin recipe using metric measurements:Ingredients:190 grams allpurpose flour150 grams granulated sugar2 grams salt10 grams baking powder80 ml vegetable oil1 large egg (approximately 50 grams without the shell)100125 ml water. 7.5 ml vanilla extract150200 grams fresh or frozen blueberriesInstructions:Preheat the oven to 200º C (400º F).Mix the flour, sugar, baking powder, and salt in a bowl.In a separate container, combine the oil, egg, and water to make one cup of liquid. Add vanilla extract.Combine wet and dry ingredients without overmixing. Fold in the blueberries gently.Fill muffin cups, sprinkle with a bit of sugar if desired, and bake for 1719:30 minutes until golden. You can check with a toothpick to see if they are cooked all the way through. Some ovens could run hotter so just see what works with regards to timings for you. Enjoy your muffins once they've cooled slightly!