Preheat the oven to 320℉/160℃. In a baking pan, spread whole almonds and bake for 12-15 minutes. Remove from the oven and cool completely before using.
Raise the oven temperature to 350℉/180℃. Line a large baking pan with parchment paper.
Using a stand mixer or hand mixer, cream butter with granulated sugar on medium-high speed until fluffy.
Add egg and extract and beat on low speed until well combined.
Sift in all-purpose flour, baking powder, and salt. Beat on low speed until well combined.
Add toasted whole almonds and fold with a spatula until well incorporated.
Divide the dough evenly into two portions. Use a spatula to scoop out the dough and place them on the prepared baking sheet. Make sure to keep them far from each other as biscotti spread during baking. Use your hands to shape them into logs. You may use a little flour to prevent the dough from sticking to your hands.
Bake for 25-30 minutes or until golden brown. Cool slightly for 15 minutes or until cool enough to handle but still warm.
Lower the oven temperature to 320℉/160℃.
Remove the logs from the baking sheet and transfer them to a cutting board. Slice the logs by pressing a sharp knife straight down into 1/2-inch (1.2 cm) thickness.
Place the slices back on the baking sheets with the cut side up. Bake for 10 minutes, and then flip the cookies and bake for another 10 minutes or until just barely golden.