Line an 8×8-in (20×20-cm) pan with parchment paper. In a large saucepan on low-medium heat, combine coconut butter or macadamia butter, syrup, sugar, (agar if using macadamia nut butter), salt, and vanilla. Stir continually as mixture heats is fully dissolved (reduce heat if mixture starts bubbling). Remove from heat and stir in cereal, making sure to fully incorporate with nut butter mixture. Transfer mixture to pan and press in evenly (use an edge of parchment paper to press without sticking). Refrigerate to cool completely, then cut into squares. Makes 16 squares.