Place the small pot over medium-low heat and add the peanut butter, maple syrup, and agave. Mix and slowly heat until the peanut butter, maple syrup, and agave are incorporated, and the mixture is smooth and runny. Add in the protein powder and mix until dissolved. If using, also add in the ground flaxseed and brewers yeast and mix until dissolved. Turn off the heat and add in the vanilla, and mix to combine.
In a large mixing bowl, add the oats and rice cereal. Mix to combine. Add in the peanut butter mixture, and mix until the peanut butter is evenly distributed and the oats and cereal are evenly coated. Set aside.
Line a 9” x 13” baking dish with parchment paper. Pour the cereal mixture into the lined baking dish and press down to create an even flat layer. Tip: Use the bottom of a glass to press the cereal mixture into an even layer. Place this in the fridge or freezer for 20 minutes to cool.
After the bars have chilled, place the dark chocolate and coconut oil in a microwave-safe dish. Microwave in 30-second intervals, mixing between, until the chocolate is melted. Pour the chocolate over the top of the bars and spread it into an even layer. If you would like, here you can top the chocolate layer with a sprinkle of flaky sea salt. Place back in the fridge or freezer for 30 minutes to chill.
Once the chocolate is set, cut the bars into 12 squares and enjoy!
Storage Instructions: Store the bars in an airtight container in a cool, dry place on your kitchen counter for up to 7 days. To keep the dark chocolate topping from becoming too soft, ensure the container is kept away from direct sunlight or any heat sources like the oven or toaster. They can also be frozen for up to 3 months; just place a piece of parchment paper between layers to prevent them from sticking together.