Start by reducing the beer down, it will reduce by half (you’ll only be using 1/3 cup of the liquid, so you could only use ½ a bottle and drink the rest while baking!) Pour beer into a pot and turn on high, stirring occasionally, and cook until it has reduced into half (about 30-40 minutes). Remove from heat and allow to cool a little.
Preheat oven to 350 degrees. Line two baking sheets with silicone baking mats or parchment paper
In the bowl of a stand mixer or with a hand mixer cream the butter and sugars, scrape the sides of the bowl and add the eggs and beat again, and then add 1/3 cup reduced stout and the vanilla extract.
In a separate bowl combine flour, baking soda, baking powder, salt and oats and stir.
Pour dry ingredients into wet and stir to combine, add chocolate chips and stir.
Scoop 1 tablespoon of cookie dough and place on lined baking sheets about 1 inch apart (I get 12 cookies per baking sheet) and bake for 8-10 minutes until edges start to brown a little (only a very little, you don’t want to over bake these because they’re a chewy cookie.) Remove from oven and allow to cool for 5 minutes on the baking sheet, then transfer to a cooling rack and allow to cool for 5 more minutes and then enjoy!