Scories de Vulcan

Lava Stones

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These lively little cookies, named for Vulcan, the Roman god of fire, have a cracked, rocky surface and crackle like a volcano as they cool. They are made in the central region of France, famous for its lava-dotted landscape. The batter is crunchy with hazelnuts and flavored with cocoa, and it must stand for at least three hours before baking. In compensation, the “stones” will keep for weeks in an airtight container. To ensure crispness, the batter uses baker’s ammonia (sold in baking supply stores and on the Internet), the same curious ingredient used in Croquets de Sancerre. Like ammonia, it stings your nose and must be used in a tiny quantity. For Coffee Stones, substitute 1½ tablespoons instant espresso powder for the cocoa.

Ingredients

  • 2 cups/280 g hazelnuts, preferably peeled
  • ½ cup/100 g sugar
  • tablespoons cocoa powder
  • 1 tablespoon/7 g flour
  • ¼ teaspoon baker’s ammonia
  • 3 egg whites

Method

Heat the oven to 375°F/190°C. Spread the hazelnuts on a baking sheet and toast them until golden, 8 to 12 minutes. If the hazelnuts were not peeled, rub them while still hot with a rough cloth to remove the skins. Let them cool completely, then grind them very coarsely in a food processor with half of the sugar—crunchy texture is important. Pulse to work in the cocoa powder, flour, and baker’s ammonia.

Set aside 2 tablespoons/30 g of the remaining sugar. Whisk 1 egg white with the remaining sugar until foamy, add it to the nut mixture in the processor, and work for a few seconds until mixed. Whisk the remaining egg whites in a bowl until soft peaks form. Gradually add the reserved 2 tablespoons sugar to the whites and continue beating until a very stiff meringue forms, 1 to 2 minutes. Add the nut mixture to the meringue and fold them together. Cover and refrigerate for at least 3 hours and up to 1 day.

When ready to bake, heat the oven to 375°F/190°C. Line a baking sheet with parchment paper. Using 2 teaspoons, set rough balls the size of a small walnut on the paper. Bake until puffed and lightly browned, 14 to 17 minutes. Let cool slightly on the paper—they will crackle like a volcano! Transfer to a rack to cool completely. When cool, the cookies will be light and crisp and have a cracked, rocky surface. They may be stored in an airtight container for a month or more.