Pre-heat the oven to 350°F.
Cream (or mix) together the butter, brown sugar, and pure cane sugar.
Add the eggs and vanilla extract to your mixture, and mix well.
Stir the baking soda into your buttermilk (or sour milk) and set aside.
Mix together the flour, salt, and ground cinnamon.
Mix the dry ingredients into the creamed mixture, alternating with the buttermilk.
Fold in the oatmeal and chocolate chips, mixing them into the dough 'til well combined.
Using a cookie scoop or a spoon, drop each cookie onto your cookie sheet, pressing/patting the cookies somewhat flat with your fingers or the bottom of a glass.
Bake for 12 to 15 minutes at 350ºF, or until the cookies turn a nice golden hue.
When you remove each batch from the oven, remove the cookies from the cookie sheet and allow them to cool on a wire cooling rack.
Serve with a nice tall glass of ice cold milk.