Heat oven to 350℉/177℃.
Line a sheet pan with parchment paper. Set aside.
In a medium bowl, combine flour, almond flour, cocoa powder, baking powder, and salt. Set aside.
In the bowl of an electric mixer, beat butter and sugar.
Add eggs and vanilla.
Beat until well combined.
Stir in flour mixture.
Add chocolate chunks. Continue at low speed until combined.
Form dough into a log.
Place on prepared pan and press down to 1 inch thick.
Bake 35 - 40 minutes, until firm.
Remove from oven and allow to cool.
Reduce oven temperature to 250℉/121℃.
Once biscotti is cool, slice horizontally into ½-inch slices.
Place slices back on sheet pan and bake for 15 minutes on each side.