Preheat oven to 350° F. Line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking powder and salt. Set aside.
By hand or using an electric mixer, cream the butter and sugar together until light and fluffy, about 2 minutes. Beat in the eggs 1 at a time, then the almond extract. Stir in the almonds. Sprinkle the dry ingredients over the egg mixture, then fold in until the dough is just mixed.
Halve the dough and turn both portions onto the prepared baking sheet. Using floured hands, quickly stretch each portion of dough into a rough 13 by 2 inch log. Place the loaves about three inches apart on the baking sheet, patting each one smooth.
Bake until the loaves until are golden and just beginning to crack on top, about 35 minutes, rotating the pan halfway through the baking time.
Cool the loaves for 10 minutes, lower the oven temperature to 325° F. Transfer the loaves to a cutting board. With a serrated knife cut each loaf diagonally into 1/2-inch-thick slices. Lay the slices about 1/2-inch apart on the baking sheet, cut-side up, and return them to the oven. Bake, turning over each cookie halfway through baking, until crisp and golden brown on both sides, about 15 minutes. Transfer the biscotti to a wire rack to cool completely.
For the glaze, whisk together confectioners' sugar, vanilla extract, butter, milk and salt until combined. Add more milk if necessary to reach desired consistency.