01 - Preheat your oven to 350°F. Line a standard 12-cup muffin tin with paper liners, ensuring each cavity is ready for batter.
02 - In a food processor, pulse the shelled unsalted pistachios until they are finely ground, taking care to stop before they form a paste. Set aside 2 tablespoons of the ground pistachios for topping.
03 - In a large mixing bowl, thoroughly whisk together the all-purpose flour, the remaining finely ground pistachios, granulated sugar, baking powder, baking soda, and salt until uniformly combined.
04 - In a separate bowl, whisk together the whole milk, plain Greek yogurt, vegetable oil, large eggs, pure vanilla extract, and natural green food coloring (if using) until the mixture is smooth and well incorporated.
05 - Pour the combined wet ingredients into the bowl containing the dry ingredients. Gently mix with a spatula or wooden spoon just until the ingredients are moistened and barely combined. Avoid overmixing the batter.
06 - Evenly distribute the muffin batter among the 12 prepared muffin cups. Sprinkle the reserved finely ground pistachios over the top of each filled cup.
07 - Bake in the preheated oven for 18 to 20 minutes, or until a wooden toothpick inserted into the center of a muffin comes out clean, indicating they are fully cooked.
08 - Allow the baked muffins to cool in the muffin tin for 5 minutes. Then, carefully transfer them to a wire rack to cool completely before serving.