Preheat oven to 350°F. Prepare a cookie sheet by lining with parchment or a silicone baking mat.
In a large bowl, mix together 1 cup chocolate peanut butter, ¾ cup brown sugar, 1 egg, and 1 teaspoon vanilla extract until thoroughly combined.
Add ⅔ cup rolled oats, ½ teaspoon baking soda, and ¼ teaspoon sea salt and mix until combined. Gently stir in ½ cup chocolate chunks until well distributed.
Using a cookie scoop, drop scoops of dough onto cookie sheet, spacing about 2 to 2 1/2 inches apart (these will spread a bit). If desired, sprinkle each cookie with sea salt for a little extra flavor.
Bake for 11-12 minutes or until the cookies are just set. Remove from oven and allow to cool for a few minutes before transferring to a cooling rack. (They will be quite soft right out of the oven but firm up a bit and become chewy once they're cooled.)