In a large bowl or the bowl of your stand mixer with paddle attached, add butter, granulated and brown sugar and beat together until creamed - about 3 minutes.
Add in your egg and vanilla and mix in. Once they have been combined, add your milk.
In a small bowl add flour, salt, baking powder, baking soda, cinnamon and all spice and whisk together.
Add your dry ingredients, plus your oats to the wet ingredients and stir together with spatula or wooden spoon.
Add your chocolate chips and mix in until evenly dispersed throughout the batter.
Scoop your cookie dough onto a lined baking sheet and cover well. Refrigerate for at least 1 hour but 3-4 hours is ideal.
Preheat your oven to 350°F.
Bake your cookies for 13-15 minutes on the middle rack of your oven. Cookies will be done but the centers will still look soft at 13 minutes. At 15 minutes they will be set but still soft, and much more browned. If baking until 13 minutes, after removing from the oven let cookies sit on the tray for about 5 minutes before transferring to a wire cooling rack.
Let cookies cool before eating, store in an airtight container for up to 5 days. Enjoy!
