Heat your oven to 170°C Fan/190°C/375°F/Gas mark 5.
Place your muffin cases into your muffin tin.
Sift your flour, sugar, baking powder and salt together into your large mixing bowl.
In a separate bowl, lightly beat together your egg, milk, oil and vanilla bean paste and then tip into your flour mixture.
Gently fold the wet mixture into the flour, using a large metal spoon or fork, stop as soon as the flour has disappeared as overmixing is a common failure of muffins. 10-15 folds should be enough.
Fold in your chopped pistachio nuts just long enough to ensure they are equally mixed in.
Fill your 12 muffin cases equally, mine took about 57 grams each, but you can just guess the weight, as long as they look roughly the same that's fine.
Bake for 20-25 minutes until well risen and golden. The muffins should bounce back up when pressed. Whilst they are baking make your sugar syrup topping.