I love the sweet, buttery flavor of pistachios and they are perfect in this muffin! Combining them with orange zest and a touch of chocolate makes these a real winner, perfect for breakfast or a midday snack.
Preheat the oven to 425 degrees F. Lightly spray two 12-cup muffin pans with nonstick cooking spray. Place a muffin liner in each of 12 of the cups, leaving 1 cup unlined next to each lined cup to promote even baking.
Whisk together the flour, brown and granulated sugars, baking powder and salt in a large bowl, breaking up any lumps of sugar; set aside.
Whisk together the eggs, buttermilk, butter, oil, orange zest and vanilla in a medium bowl.
Make a well in the center of the dry ingredients and pour in the liquid ingredients. Stir gently with a rubber spatula until fully combined. Reserve 1/4 cup of the pistachios and 1 tablespoon of the chocolate chips for topping, then fold the rest into the batter. Divide the batter among the 12 lined cups, leaving the unlined cups empty. Spread the batter with a spoon to the edges of the paper liners.
Sprinkle the reserved pistachios and chocolate chips evenly over the muffins, then sprinkle the tops with the turbinado sugar.
Place the muffin pans in the oven and reduce the oven temperature to 375 degrees F. Bake until a toothpick inserted in the center of the muffins comes out with a few moist crumbs attached, 26 to 28 minutes. Let the muffins cool in the pans on a wire rack for about 10 minutes. Carefully remove each muffin and let cool on the rack.
When measuring flour, spoon it into a dry measuring cup and level off the excess. (Scooping directly from the bag compacts the flour, resulting in dry muffins.)