Preheat oven to 325 degrees F.
Line a 8x8 pan with parchment paper (make sure its long enough for the ends to overhang) and set aside.
In a large bowl, combine the oats, brown rice cereal, cinnamon, flax meal, chia, sunflower seeds and salt. Mix well.
In a smaller bowl, whisk together the tahini, vanilla and brown rice syrup. If mixture is really thick, add 1 tbsp of non-dairy milk at a time and whisk again until the mixture is pourable.
Pour the wet ingredients into the dry ingredients while continually stirring to mix well. Add the chocolate chips, if using, and mix well.
Once everything is incorporated well, pour the mixture into the prepared 8x8 pan. Press the mixture down into an even layer with your fingers. It helps to slightly wet your hands before pressing.
Bake for 25-28 minutes until golden on the top and starting to firm up. The bars will continue to firm up as they cool.
Cool in the pan on a wire rack for 10-15 minutes until you can lift the bars out easily by holding onto the ends of the parchment paper. Continue to cool the bars on the parchment paper on a wire rack for another 10 minutes. Cut into bars or squares and continue to cool if they still feel soft.
Once the bars are completely cool, whisk the dark chocolate chunks in a double boiler until melted. Add 1 tbsp of non dairy milk at a time until desired consistency is reached. You want it thin enough to drizzle, but thick enough to set up on the bars. Drizzle onto the bars.