Preheat oven to 350F and grease a 9 x 9 baking dish or line with parchment paper.
Combine butter and ¾ cup chocolate chips in a microwave-safe bowl. Microwave for 30 seconds at a time, stirring in between each interval until fully melted.
Add eggs and vanilla extract, whisk to incorporate fully.
Add coconut sugar, cocoa, oat flour, and salt and mix until the batter is smooth. Fold in ¼ cup chocolate chips into batter.
Spread the batter out in the baking dish (it will be thick) until even.
Bake for 25-35 minutes or until an inserted toothpick comes out clean. I set the timer for 25 minutes and check it every 3 minutes after that.