Preheat oven to 350°F (175°C) and line an 8x8 inch baking pan with parchment paper leaving an overhang on two sides.

In a large mixing bowl, whisk together the rolled oats, protein powder, flaxseed, salt, and cinnamon.

In a small microwave-safe bowl, combine the peanut butter and honey and heat for 30 seconds until softened; stir in the vanilla extract.

Pour the liquid mixture over the dry ingredients and stir until a crumbly dough forms.

Add almond milk one tablespoon at a time until the mixture is moist enough to hold together when pressed.

Fold in the dark chocolate chips until evenly distributed.

Transfer the mixture to the prepared pan and press down very firmly using a flat spatula to ensure the bars hold together.

Bake for 18 to 20 minutes until the edges are just beginning to turn golden brown.

Remove from the oven and allow to cool completely in the pan for at least 1 hour to set.

Lift the parchment paper to remove the block and slice into 12 rectangular bars.