Grind the nuts in 2 batches - 1/2 fine grind and 1/2 course grind (to roll biscotti in later). Whisk eggs with sugar til frothy; stir in butter and lemon zest. Sift dry ingredients and add to finely ground nuts, then add egg mixture to dry mixture. Shape dough into 2 logs and bake at 350 for 25 minutes. Cool and slice 1/4" thick. Bake at 250 until dry. Melt chocolate w/oil. Dip one end of each cookie in chocolate and roll in coarse nuts.