You want to chop the pistachios very fine, into a grainy, sand-like consistency. You can use a mini-chopper for the job, but I find it very therapuetic to do it by hand. I also only have one madeleine pan, so I just wash it as soon as the first batch is done, then dry it thoroughly before greasing and flouring for the second batch. It sounds like more of a pain than it is in actuality.
16 tablespoons (6 ounces) unsalted butter, plus more for greasing pans
4 large (200 grams) eggs
Pinch of fine sea salt
2/3 cup (135 grams) granulated natural cane sugar
1/3 cup (41 grams) raw pistachios, chopped very fine
2/3 cups (96 grams) flour, plus more for coating pans
2 tablespoons (14 grams) good-quality dark cocoa powder
1 teaspoon pure vanilla extract
Confectioner’s sugar, for dusting (optional)
Preheat the oven to 350ºF.
In a small pot, over medium-high heat, melt the butter until it becomes brown and fragrant, but not burned, about 10 minutes. Remove from the burner, and set aside to cool while you proceed with the rest of the recipe.
In a medium bowl, whisk together the pistachios, flour and cocoa until well mixed; set aside.
In a stand mixer or deep bowl, beat the eggs on high speed until they are thick and have tripled in volume, about 4 minutes. With the mixer still on high speed, slowly pour in the granulated sugar. Once all the sugar has been added, beat for 2 more minutes.
Lightly sprinkle the flour mixture over the egg mixture. Using a rubber spatula, fold until the batter is just mixed. Pour in the melted butter and gently fold, just enough to mix the batter until there are no pools of melted butter. Let the batter rest for 15 minutes.
Meanwhile, generously grease the madeleine pans with butter—I mean really generously, get into all the grooves as well as the top rim of the pan. Coat with flour, tapping off any excess.
Gently spoon batter into one of the prepared pans, filling the molds about 2/3—do not overfill. Bake for 14 minutes, remove from oven and vigorously tap (code for bang) pan on the counter, which will release the madeleines from the pan. Set on a wire rack to cool completely.
Fill the second pan with batter, then bake and remove from pan as directed above. When cool, sift Confectioner’s sugar over the madeleines, if desired, before serving.