Preheat the oven to 350 degrees.
Cream together the butter and sugars in a large bowl for about 2 minutes, until light and creamy.
Mix in the eggs and vanilla extract.
Dump in the flour, cocoa powder, salt, and baking soda and stir together until everything is mixed.
Fold in the mint chips.
Scoop cookie dough by the tablespoonful onto a lined baked sheet.
Bake cookies for 7-9 minutes until they start to look crackly and down on the top.
Allow cookies to sit on the cookie sheet for about 3 minutes before removing to a cooling rack, as they will continue to cook while on the pan.