Heat oven to 350°F (190 C) and line a cookie sheet with parchment paper.
In bowl of stand mixer, beat butter and sugar until fluffy using whisk attachment.
Add in eggs, 1 at a time continuing to mix on medium high.
Pour in vanilla.
Take a separate medium bowl and whisk together flour, baking powder and salt.
Spoon flour mixture into butter mixture and whip together until combines.
Remove bowl from stand mixer.
Fold in pecans and walnuts with a spatula.
Dump batter onto lightly floured surface and form into a ball with your hands.
Take a bench scraper or sharp knife and cut in half.
Place each half onto baking sheet and flatten out into two 12 inch logs.
Bake for 35 minutes.
Remove from oven and let cool for 15 minutes.
Take a serrated bread sharp knife and slice each log diagonally into ½ inch pieces.
Lay the slices on their sides back onto the baking sheet.
Bake for 15 minutes and then flip over to bake for a remaining 15 minutes, until golden brown on edges.
Cookies can be slightly soft in the center, but will harden as they cool.
Let Biscotti slices cool on rack completely before adding chocolate.
Melt white chocolate and drizzle over each cookie.
Place tray in the fridge for 10 minutes to help white chocolate set.
Store in an airtight container.
Dip Biscotti in warm coffee or hot chocolate!