Preheat the oven to 325°F (165°C) and line a large baking sheet with parchment paper.
Beat butter and sugar together with a stand or handheld mixer for a few minutes, until light and fluffy.
Beat in the eggs, one at a time, and then add the almond extract.
In a separate bowl, whisk together the flour, baking powder, and salt, and then gradually mix into the butter mixture.
Fold in the almonds and mix until combined. You will have a very soft dough. Cover and let the dough chill in the refrigerator for 15 minutes.
Once chilled, divide the dough into 3 portions, roll each portion into a log about 1 ½ inch (4cm) in diameter, and place on your prepared baking sheet about 3 inches (8cm) apart.
Bake for about 40 minutes, or until slightly browned.
Let cool for just 5 minutes, and then, while the logs are still warm, cut them on the diagonal about 1 inch (2.5cm) thick and place them back on the baking sheet, cut side up.
Bake for 5-10 minutes, just barely golden, and then flip the cookies and bake the other side for 5-10 minutes, until just barely golden. Let cool on wire racks.
Store biscotti in an airtight container at room temperature for up to 3 days or freeze in an airtight container for up to 2 months.