In a medium bowl, whisk the flour, cinnamon, baking soda, and salt together. Set aside.
Place your softened butter into a large bowl and beat it with a hand mixer on medium speed for about 2 minutes until light and fluffy.
Add the brown and white granulated sugar to the creamed butter and beat on medium-high speed until creamed. Add the first egg and whisk into the mixture. Add the second egg and whisk it in as well. Add the vanilla extract and beat the mixture for another minute until light and fluffy scraping the sides down as needed.
Begin to pour the dry ingredients into the wet ingredients and mix on low speed with your hand mixer until they are combined together. While still running on low speed add the oats. With a silicone spatula stir in the semi-sweet chocolate chips. Your dough will be quite thick at this point.
Optional: chill the dough for 1 hour.
Preheat oven to 350℉/175℃/Gas Mark 4.
Line the baking sheets with parchment paper. Scoop the cookie dough onto the baking sheets and bake for 13-14 minutes. Press more chocolate chips into the tops of the cookies if you want to before baking. The centres of the cookies will look a bit soft, but the edges will look crispy and set.
Remove from the oven and let sit at room temperature for about 5 minutes until the cookies have set a little more and can be transferred to a wire rack without falling apart. Once the 5 minutes is up and the cookies can be lifted, transfer them to a wire rack to continue to cool.