Place all nuts, sunflower seeds and chia seeds into a large baking tray and mix. Bake for 5 minutes.
Add coconut and sesame seeds and mix. Bake for a further 3 minutes.
Set aside to cool. Reduce oven temperature to 160°C.
Blitz approximately 1 cup of the mixture in a food processor until a coarse flour forms, then place into a large bowl with the rest of the roasted ingredients. Add dates (if using) spice and salt. Combine well.
Place the syrup and oil into a small saucepan, heat slowly on LOW heat, stirring until the ingredients are well combined and just bubbling.
Pour over dry ingredients and mix to combine.
Press into a lined 30cm x 20cm sandwich baking tray so the top is smooth and flat. Use a second sheet of baking paper to press down if the mixture is too sticky.
Bake for 15 minutes or until small bubbles start forming.
Set aside to cool.
Cut into 18 bars and store in an airtight container.