Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners.
In a bowl, whisk together flour, sugar, baking powder, salt, and chopped pistachios.
In a separate bowl, whisk the egg, milk, oil (or butter), and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and gently mix until just combined. Do not overmix.
Divide the batter evenly among the muffin cups.
Bake for 18-20 minutes, until the tops are lightly golden and a toothpick comes out with a few moist crumbs.
Let muffins rest in the pan for 10 minutes, then transfer to a cooling rack.