In a large mixing bowl, combine the peanut butter and honey (or maple syrup) until well mixed.

Add in the vanilla extract and salt, and stir until fully combined.

Gradually mix in the rolled oats and protein powder until the mixture is thick and well combined.

If desired, fold in dark chocolate chips and chopped nuts for added texture and flavor.

Line an 8x8-inch baking dish with parchment paper for easy removal.

Press the mixture firmly into the prepared baking dish, spreading it evenly.

Refrigerate for at least 1 hour to allow the bars to set.

Once set, remove from the dish and cut into bars or squares.

Store the bars in an airtight container in the refrigerator for up to a week.