Preheat the oven to 350°F and line a baking sheet with parchment paper. If you decide to go the skillet cookie route, I recommend lightly greasing your skillet or baking dish.
In a medium heat-safe bowl, melt the butter in the microwave. Whisk the sugars into the melted butter until smooth and creamy, at least one minute of whisking.
Add in the eggs and vanilla and mix well, then stir in the flour, cinnamon, baking soda, and salt until just combined into a dough.
Gently stir in the chocolate chips and blueberries, trying to keep the berries mostly intact.
Dollop the dough onto the cookie sheet, you want medium-size cookies. If making a skillet cookie, spread the dough evenly in the prepared skillet. In both cases, sprinkle with flaky sea salt.
Bake for 12 to 15 minutes, depending on size. You want them golden on top and crisp around the edges. If doing as a skillet cookie (or a mini-skillet), you'll need 20+ minutes. If making cookies, I prefer these to be fully baked vs. under-baked, but if you're doing a skillet cookie then a bit of gooey is a good thing.