Preheat oven to 350 degrees F. Spread almonds in an even layer on a baking sheet and toast in the oven for 12-15 minutes, stirring halfway through. Remove from oven and coarsely chop, then set aside.
In a large bowl, beat the eggs and sugar for 3 minutes until light. Add the almond and vanilla extract and beat again.
In a large bowl, whisk together the flour, baking powder, and salt. Add the egg mixture and chopped almonds, stirring just until combined. Turn onto a lightly floured surface and knead a couple of times until no streaks of flour remain, then divide into two logs.
Transfer the two portions of dough to a parchment or silpat lined baking sheet and pat into two rectangles, roughly 9x3-inches each and about ½ inch thick. Make sure there is space between the two for them to spread, then bake for 25-30 minutes until lightly brown around the edges and on the bottom.
Remove from oven and cool for 5 minutes, then transfer to a cutting board and slice into 9-10 slices, about ¾-inch thick, using a sharp knife. Arrange cut-side down on the baking sheet and return to the oven. Bake for 10 minutes, flip to the other cut side, then bake for another 10 minutes.
Remove from oven and cool completely.
To decorate, melt the chocolate carefully in the microwave using short 20 second bursts of heat. Stir between each burst of heat until melted. Drizzle or dip the cooled biscotti pieces if the melted chocolate, then sprinkle with additional chopped toasted almonds, if desired.