Preheat your oven to 350°F.
Line baking sheets with parchment paper. Set aside.
In a double boiler (a glass bowl over a sauce pan of boiling water) or in a microwave- safe bowl, add your chocolate chips and butter.
Heat over medium heat until melted together, stir frequently. If using the microwave, heat in 30 second intervals. Set aside to cool.
In a large mixing bowl, combine eggs, brown sugar and granulated sugar.
Using a mixer, whip the eggs and sugars together for about 3 minutes on a medium-high speed.
Turn our mixer to low, add in your slightly cooled chocolate and butter mixture.
Add in the vanilla extract.
Once those are well combined, add in your flour, cocoa powder, baking powder and salt.
By hand using a spatula, fold in your walnuts.
Using a medium cookie scoop, scoop out batter on to the parchment lined baking sheet. Leave a bit of room in between each drop so that they don't spread into each other. I typically fit about 6 cookies on 1 sheet.
Bake for about 12 - 14 minutes. Let them cool on the baking sheet for about 10 minutes before moving them to a cooling rack.