Preheat the oven to 350°F (180°C) and line an 8-inch x 8-inch brownie pan with parchment paper. Slightly oil the pan to prevent sticking, then set aside.

In a microwave-safe bowl, melt ⅓ cup of the sugar-free chocolate chips together with the coconut oil. Allow this mixture to cool for a few minutes at room temperature.

In a medium bowl, whisk together the oat flour, unsweetened cocoa powder, granulated sweetener, baking powder, and salt until well combined.

In a separate large bowl, whisk the Greek yogurt, egg, vanilla extract, almond milk, and the cooled melted chocolate mixture until smooth.

Sift or gradually add the dry ingredients into the wet mixture, gently folding with a silicone spatula until just combined without overmixing.

Stir in the remaining ⅓ cup of sugar-free chocolate chips, distributing them evenly throughout the batter.

Pour the brownie batter into the prepared pan, spreading it evenly. Bake for 20 to 23 minutes or until a toothpick inserted in the center comes out clean.

Remove brownies from the oven and place on a cooling rack. Let cool completely for about an hour before cutting into 16 squares for serving.