Guinness Mixture

1. In a large saucepan over medium heat cook the Guinness and brown sugar together for 15-20 minutes (please note depending on the size of your saucepan the cooking time may reduce or increase). The mixture will reduce to 1/3 cup. Set aside to cool, I place mine in the freezer to speed things up.

Cookie Dough

1. In the bowl of an electric mixer with the paddle attachment or a large bowl with a handheld electric mixer beat the butter for 2 minutes, add sugars, and beat for another 2 minutes. Add the whole egg and mix to combine then add the egg yolk and vanilla mix for 2 minutes until fully incorporated. Mix in Guinness mixture.
2. In a medium bowl sift together flour, cocoa powder, baking soda, and salt.
3. Slowly add dry ingredients into wet ingredients, until just combined. Fold in chocolate and scoop balls onto a parchment-lined baking sheet that is wrapped tightly to chill for at least 2 hours or up to 2 days. I like to use this medium cookie scoop for evenly sized cookies, it's 1 1/2 tablespoons of dough.
4. Preheat to 350F/180C and line a baking sheet with Silpat liner or using parchment paper. Place chilled cookie dough balls on a prepared baking sheet two inches apart. Bake for 8-10 minutes, the dough will be just set but take it out of the oven and let cool for 10 minutes before transferring to a wire rack. Store leftovers in an air-tight container for up to 5 days.