To achieve the most volume, whisk egg whites in a metal bowl set over a pot of simmering water until just warm to the touch.
- 1 3/4 cups sliced almonds (about 5 1/2 ounces)
- 1 cup confectioners' sugar
- 2 large egg whites
- 1/2 teaspoon pure almond extract
Preheat oven to 350 degrees. Spread almonds in a single layer on a rimmed baking sheet, and toast in oven until lightly browned and fragrant, 7 to 9 minutes. Remove from oven; let cool.
Combine almonds and sugar in the bowl of a food processor fitted with the metal blade, and grind to a fine powder. Transfer to a medium bowl. In a separate bowl, beat egg whites until stiff peaks form. Fold egg whites into almond mixture; fold in almond extract.
Line a baking sheet with parchment paper. Transfer almond mixture to a pastry bag fitted with a 1/2-inch plain tip. Pipe twenty 2-inch rings onto prepared sheet, about 1 inch apart. Bake until golden brown and firm to the touch, about 25 minutes. Remove from oven, and immediately transfer to a wire rack to cool completely.