Add all of the squares ingredients (except for the buckwheat and quinoa and toppings) to a food processor. Mix until the mixture is super smooth and creamy. Taste the mixture to see if it needs to be adjusted. Add more cacao powder if you like a stronger chocolate flavour, etc. It should be a thick and creamy texture.
Measure the buckwheat and quinoa and pour into a medium sized mixing bowl. Add the chocolate mixture to the mixing bowl and stir carefully into the buckwheat and quinoa until everything is evenly combined and has an even coating of the wet mixture.
Press the mixture into a square prepared baking pan (I lined mine with parchment paper). Press down so the mixture is spread out evenly and smoothly. Sprinkle optional cacao nibs and toasted sesame seeds over the top for decoration and extra flavour. You can drizzle more tahini on as well but then the squares will become more sticky.
Place the squares in the freezer to all the dessert to set completely and firm up for about 30 minutes.
Cut the treat into 9 evenly sized squares. Store in an airtight container in the fridge, or freezer.