For the macarons:
1. Preheat oven to 150 degrees Celsius (fan). Roast sunflower seeds on a baking tray that has been lined with aluminium foil for about 10 minutes and let cool completely. Turn the heat down to 140 degrees Celsius.
2. Blitz cooled roasted sunflower seeds and icing sugar in the food processor until you get a finely ground mixture. This took about 1 minute for me. Sift this sunflower seed flour into a bowl. At this stage, you will have some residue that is not finely ground, so just pop that back into the processor and blitz for another 30 seconds. Sift this mixture again into the bowl. It is crucial to not over-blitz them, as the heat will cause oils to be released; this wets the mixture and creates tiny lumps, something that you don't want when you make macarons. I had about 20g of mixture that was not finely ground, and I simply chucked these away.
3. In a separate bowl, whisk egg whites and egg white powder till soft peaks are formed. Whisk in caster sugar until stiff peaks form.
4. To the egg white mixture, fold in dry ingredients from Step 2 in 1/3 portions to combine. Once the last portion of dry ingredients are added, fold in the mixture more vigorously. Test the consistency from time to time by lifting a generous dollop of macaron paste and dropping it into the mixing bowl. If the macaron paste does not settle smoothly after 30 seconds, continue folding the paste. If the macaron paste smooths out too quickly before 30 seconds are up, you’ve gone too far.
5. Pipe out the shells onto a baking sheet lined with parchment and leave them to rest for 15 minutes before baking.
6. When a 'skin' is formed (touch the shells and the batter should barely stick to your fingers), bake for 15 minutes. You might need to turn the tray around halfway through baking, if your oven has hot spots.
7. Cool parchment of baked shells on cooling rack. Unmould when the shells are completely cooled.

For the ganache:
1. Place white chocolate and cream in a double boiler and heat over barely simmering water till chocolate melts. Stir continuously as you melt the chocolate.
2. Let the ganache cool slightly and stir in the salt and chopped black truffles.
3. Refrigerate ganache till it sets to a pipe-able state and fill the cooled macaron shells.

Refrigerate the filled macs to allow flavours to mature, then let them come to room temperature before serving.