Line the bottom of a 9x9 inch (22x22cm) square pan with parchment paper. Set aside.
Put 1/2 oats into the food processor and pulse for 2 second to cut up oats in smaller pieces. Combine with the rest of oats in one larger mixing bowl.
In the separate bowl, mash banana with the fork. Add syrup or honey and vanilla extract and softened peanut butter and mix well until you get a smooth mixture.
Add peanut butter banana mixture into oats and stir until evenly combined.
In meanwhile melt dark chocolate chunks or chocolate chips in microwave or using the stove. Let it cool for few minutes then spread the melted chocolate on top of the oats.
* For gluten-free version make sure you use certified gluten-free products. ** For VEGAN version use vegan dark chocolate chips. Keep in an airtight container refrigerated for up to 1 week. Place in ziplock bags and freeze up to 3 months. As a measure, I used UScup (240ml).