Stir together sugar, butter, brandy, and extracts in a large bowl, then stir in almonds and eggs. Stir in flour, baking powder, and salt until just combined.
Chill dough, covered, 30 minutes.
Preheat oven to 350°F with rack in middle.
Using moistened hands, halve dough and form 2 (16-by 2-inch) loaves on an ungreased large baking sheet.
Bake until pale golden, about 30 minutes. Carefully transfer loaves to a rack and cool 15 minutes.
Cut loaves into 3/4-inch slices with a serrated knife.
Arrange biscotti, with a cut side down, on a clean baking sheet and bake until golden, 20 to 25 minutes. Transfer to rack to cool completely.
Biscotti improve in flavor if made 1 to 2 days ahead. Keep in an airtight container at room temperature.Servings: 42 cookies