Step 1

Preheat oven to 350°F.

Step 2

Line baking sheet with parchment paper.

Step 3

Combine flour, cocoa powder, salt and baking soda in medium bowl; stir to combine. Set aside.

Step 4

Combine butter and unsweetened chocolate in large microwave safe bowl. Microwave on high for 30 seconds; stir well. Repeat heating at 10 second intervals, stirring in between, until butter and chocolate is completely melted and smooth.

Step 5

Add brown sugar, granulated sugar, eggs and vanilla; whisk well to combine.

Step 6

Add flour mixture; stir to combine. Fold in chocolate chips and walnuts.

Step 7

Scoop heaping tablespoons of dough onto prepared cookie sheet. Chill in refrigerator 10 minutes.

Step 8

Bake for 12 minutes or until set. Cool on pan 2 minutes; transfer to wire rack.