Combine 8 tablespoons of melted butter, 1 cup of sugar, 3 large eggs and 2 teaspoons of vanilla extract in a large bowl and mix until fully combined
Add 1 teaspoon of baking powder, 1/2 teaspoon of sea salt, 1/3 cup of unsweetened cocoa powder, 2 cups of all purpose flour and 1 tablespoon of instant espresso powder and mix until all of the ingredients are fully incorporated
Fold in 1/2 cup of chopped dark chocolate until evenly distributed
Cover the bowl and chill in the refrigerator for 3 hours or the freezer for about 45 minutes
Preheat your oven to 350 degrees
Transfer the dough onto a baking sheet lined with parchment or a silicone baking mat
Divide the dough in half and gently shape both portions into a roughly 8” x 4” rectangle
Brush each portion with a whisked egg
Bake at 350 degrees for 22-24 minutes or until the dough feels lightly set in the center
Transfer the baking sheet onto a cooling rack and allow the dough to cool for 10 minutes
Carefully transfer the dough onto a cutting board using the parchment paper or silicone mat
Cut 3/4-1 inch strips out of the dough starting on the short end using a sharp serrated knife (photos above)
Place each piece, cut side down onto a baking sheet
Bake in the 350 degree oven for an additional 8-10 minutes on each side
Transfer the biscotti to a cooling rack to cool while you prepare the chocolate garnish
Melt 1 cup of dark chocolate in a shallow wide bowl
Dip the tops of each biscotti into the melted chocolate and sprinkle with flaky sea salt
Store in an airtight container for up to 30 days