Preheat the oven to200°C / 400°F.
Prepare a muffin pan for12 muffins with their paper wrappers (see notes 2)
In a large bowl sift the flour, baking powder, cinnamon, ginger and salt. Mix briefly.
Add the chopped hazelnuts and mix. Set aside.
In another bowl add the eggs, vanilla and sugar. Whisk until incorporated.
While continuing to whisk, add the melted butter until incorporated.
Add the grated zucchini and incorporate with a spatula.
Transfer the liquid ingredients over the dry ingredients and carefully incorporate until all the flour is moistened.
Distribute the mixture in the muffin tin.
Optionally add more chopped hazelnuts (into smaller pieces) on top of each muffin and sprinkle with brown sugar as well.
Bake in the preheated oven for approximately 15 to 17 minutes.
Once ready, remove from the oven and let stand for 10 minutes at room temperature.
Unmold and let themuffins rest on a wire rack until they have completely cooled to roomtemperature.