Crush coriander, cumin and fennel seeds in a spice grinder or mortar and pestle and mix with curry powder.
Heat olive oil in a medium fry-pan on low-medium heat. Add garlic, spice mixture, lemon zest and rosemary, and cook, stirring, for 1-2 minutes until fragrant.
Add nuts and continue cooking, stirring to coat everything nice and evenly, for a few minutes to lightly toast the nuts.
Add smoked paprika, sea salt, chilli (if using) and maple syrup – the maple syrup will bubble away. Stir to coat everything and keep cooking for a further 1 minute or so. Turn off heat and transfer to a dish or bowl to cool completely and go crunchy before storing. Store in an airtight container in the fridge for up to 4 weeks.