Spread the almonds on a rimmed baking sheet and toast, tossing occasionally, until golden, 4 to 5 minutes; let cool. (Or, toast on the stove top in an iron skillet ~ stir constantly til golden. Be careful not to burn them!).
In a food processor, pulse ½ cup of the almonds with ½ cup of the brown sugar until the almonds are finely ground. Transfer to a medium bowl and stir in the flour, baking soda, and salt.
With an electric mixer, beat the butter and the remaining ½ cup brown sugar at medium speed until creamy, about 2 minutes. Add the egg, vanilla extract, and almond extract and beat to combine. Reduce the mixer speed to low and gradually mix in the flour-nut mixture just until combined (do not overmix). Gently fold in the remaining ½ cup almonds.
Form the dough into two 12-by-1½-inch logs. Refrigerate, tightly wrapped, until firm, about 2 hours or up to 2 days.
Heat oven to 350° F with the racks in the upper and lower thirds. Working with 1 log at a time (keep the other chilled), cut it into ¼-inch slices and place the slices on 2 baking sheets, spacing them 2 inches apart. Bake, rotating the baking sheets halfway through, until golden, 9 to 11 minutes. Transfer to a wire rack to cool.
Keep the cookies at room temperature in an airtight container for up to 5 days.