In a medium saucepan, melt the butter until melted, over medium-low heat. Remove from the heat.
Add the dark brown sugar and granulated sugar and stir until sugars are incorporated and smooth. Chill the mixture for 10 minutes. (Do not skip this step. You can also transfer the mixture to a different bowl so that it is no longer being heated from the pan.)
Remove the cookie dough from the refrigerator and stir in the eggs and vanilla.
Add the flour, oats, baking soda, 1/2 teaspoon salt, and cinnamon and mix together with a spoon.
Gently fold in the white chocolate chips and chocolate chips.
Chill dough until it is firm enough to be hand rolled, about 30 minutes in the fridge.
Roll by hand into 24 medium-size balls or use a scoop, and place on a parchment lined cookie sheet.
Refrigerate for 30 minutes or freeze for 10 minutes.
While the dough is chilling, heat the oven to 325 degrees F.
Bake for 12 to 14 minutes, or until the edges just start to turn golden. (Do not overbake)