(*Optional) Add the quick oats to a blender or food processor. Place the lid on and grind at high speed until the oats turn into a fine powder. Set it aside. *You can skip this step if you prefer more oat textures in the brownie bites.
Preheat oven to 340F (170C). Lightly grease a mini muffin pan with oil.
Place the sugar-free chocolate chips in a microwave-safe bowl and cover it with a saran wrap. Microwave for 1 minute. Remove from the microwave and stir. Continue to microwave in 30-second increments, stirring frequently, until the chocolate has fully melted.
Add erythritol into the melted chocolate and mix until fully combined.
Add yogurt into the melted chocolate mixture and mix well.
Add eggs into the melted chocolate mixture and mix until fully combined.
Add the powdered oats, baking powder, whey protein powder, and chopped walnuts and mix until well combined.
Pour the brownie mixture into a mini muffin pan using a spoon or a piping bag, filling the tins almost all the way full. Bake for 10-12 minutes or until a toothpick inserted into the center of the brownies comes out with moist crumbs and not completely dry.
Allow brownie bites to cool in the pan and remove them out of the muffin pan.
(Optional) Sprinkle with some coarse kosher salt and enjoy!