Chocolate Madeleines

• ½ cup water
• ¼ cup unsweetened imported cocoa powder
• 3 ounces bittersweet chocolate, melted
• 2 teaspoons pure vanilla extract
• ¾ stick (3 ounces) unsalted butter, softened
• ¼ cup plus 3 tablespoons crème fraîche or sour cream
• 2 extra-large eggs
• 1 extra-large egg yolk
• ¾ cup granulated sugar
• 1 cup plus 5 tablespoons unbleached pastry flour or unbleached all-purpose flour
• 1½ teaspoons baking soda
• 1 teaspoon baking powder
• ½ teaspoon kosher salt

In a small saucepan over medium heat, whisk together the water and cocoa powder. Bring to a boil, whisking constantly. Remove from the heat and whisk in the chocolate, vanilla extract, and butter. Stir in the crème fraîche and set aside.

In the bowl of an electric mixer fitted with the whisk attachment, whip the whole eggs and egg yolk with the sugar on medium-high, 5 to 8 minutes, until thick and mousselike. Remove the bowl from the mixer and whisk in the chocolate mixture.

Over a medium mixing bowl, sift to combine the flour, baking soda, baking powder, and salt. In 3 additions, gently fold the flour mixture into the egg mixture, deflating the batter as little as possible.

Chill at least 24 hours or up to 3 days.

Adjust the oven rack to the upper position and preheat the oven to 375 degrees.

Pipe or spoon the batter into the prepared molds, completely filling each section to the top.

Bake 12 to 18 minutes, until springy to the touch.

Allow to cool a few minutes before unmolding. Place on a platter, scalloped side down.