Combine 1 ¼ tablespoon of boiling water with chia seeds to make a chia egg. Stir very well, then set aside for later. In the meantime, melt the butter in a large mixing bowl and add in the brown and white sugar. Mix the butter and sugar mixture until it thickens slightly and sugar has partly dissolved.
Add the vanilla and chia egg to the butter mixture and stir.
In a separate bowl mix together the flour, bicarb, corn starch, salt, and matcha powder.
Gradually add the flour mixture to your butter mixture and stir with a spatula until just combined. Chop your hazelnuts and white chocolate and fold into the matcha cookie dough.
Cover your bowl with clingfilm and let the dough rest in the fridge for at least an hour.
After an hour, scoop the mixture into 8 equal balls and place on a baking tray.
Bake for 10-12 minutes at 180°C/356°F (fan oven) and let cool on baking tray. If not using a fan oven, bake at 200°C/392°F.
Notes
Don't forget to MELT your butter!
Use BOTH white and brown sugar for optimal results.
Don't be tempted to bake straight away before refrigerating. This is an important part of the recipe so don't skip it.
Don't think you need to bake the cookies until they're hard. Bake until the edges are crisp, but the middle is still soft. This way you'll get a gooey, rich, moist cookie.