Roast the hazelnuts and pistachios for 8 minutes at 180°C fan.
Heat up a fry pan and add the coriander seeds and peppercorns. Toast them for about 2 minutes until fragrant. Shake the pan occasionally to ensure even toasting.
Transfer the toasted coriander seeds and peppercorns into a mortar and pestle. Crush and grind the seeds.
Once roasted, add the nuts into the mortar and pestle. Crush and grind the nuts until they're made up of small pieces and are combined with the coriander and peppercorn pieces.
Add the cumin seeds, fennel seeds and sesame seeds to the heated fry pan. Toast for 2-3 minutes, shaking the pan every now and again. Once toasted, add the seeds to the mortar and pestle. Roughly the seeds and mix them with the rest of the ingredients.
Finally, add the salt flakes and combine them with the rest of the ingredients.
Transfer the dukkah into a sealable glass jar and store it in a cool, dry area.