Preheat oven to 300 F. Prepare a large baking pan with parchment paper or silicone baking mat.
Using a mixer with the paddle attachment, cream together butter with both sugars until fluffy.
Add eggs, vanilla extract, and espresso powder. Mix until well combined.
Gradually add flour, baking powder, and salt into mixture. Mix until well incorporated.
Fold in the macadamia nuts into the mixture.
Dust your hands with flour and shape the dough into a log form on the prepared baking sheet. Place in oven on middle rack and bake for 25 minutes or until golden brown and firm to touch. Allow to cool for 10 minutes. Leave oven on.
With a serrated knife, slice each log into 1/2-3/4 inch thickness. Place the slices cut side up onto the baking pan again.
Bake for 10 minutes. Then remove the pan and flip the biscotti to the opposite side. Bake for another 10 minutes.
The slices should be lightly toasted at this point. Remove from oven and allow to cool completely.
Either dip the biscotti into melted chocolate or use a rubber spatula to spread the chocolate on the bottom of each biscotti. You can also drizzle the chocolate if desired.
Allow chocolate to harden, and then serve with a fresh cup of coffee! Keep remaining biscotti in a sealed container at room temperature.