Heat a small sauce pan on the stove and add the milk stout. Bring to a simmer and reduce by half.

Put melted butter and sugars into a mixer and stir until combined. Next add in the reduced milk stout and the beaten egg and continue to mix well.

Add in the flour and baking soda; mix until combined into a cookie dough. Fold in the chocolate chips.

Put all of the dough into a air tight container and let it chill in the fridge for at least an hour.

Once chilled, pre-heat the oven to 325 degrees F, and roll cookie dough into balls. Roll even sized balls, and then press one ball on top of another and lightly flatten them with the palm of your hand. This gives the cookie a chewy inside and a crispy outside. Put cookies onto a parchment paper lined cookie sheet.

Bake in the preheated oven for 12 - 15 minutes or until lightly golden brown on the top. Leave cookies on cookie sheet for 3 - 5 minutes before transferring to a cooling rack.