Preheat the oven to 375°.
Cream the *softened butter with both the brown and the white sugar together in a **stand mixer with the paddle attachment. Let it mix on medium speed until the color has lightened and it is whipped and fluffy-looking, about 1-2 minutes (see photo above for example).
Using a rubber spatula, scrape down the sides of the bowl, and give it a good mix scraping the bottom of the mixing bowl as well. Add the eggs. Mix until well incorporated. Scrape down the sides again.
Add the vanilla, salt, and baking soda. Mix until incorporated. Scrape down the sides again. Also, scrape the bottom of the bowl to give it all a good mix by hand to make sure the dough is smooth and the ingredients are evenly distributed.
Add the flour 1 cup at a time, mixing until just combined.
Add the oats and chocolate chips. Mix until just combined throughout the dough. Do not over-mix or your cookies will turn out tough.
Line a large cookie sheet with parchment paper. Using an ice scream scoop, scoop 8 evenly shaped mounds of dough onto the cookie sheet. If you do not have an ice cream scoop, make each dough ball roughly 3 tablespoons.
Bake for 14 minutes, until lightly browned on edges. Cool on cookie sheet for 5 minutes, then transfer to a cooling rack.
Store the extra dough in a sealed container in the fridge for up to 2 weeks.