In a bowl, combine the sugar, ginger, walnut flour, all-purpose flour and corn flour with salt.
Cream the butter and the egg yolk together until fluffy.
Add in the flour mixture, about 2 tbsp at a time, and mix gently. Don't mix too much so that the cookie remains flakey.
When flour and butter mixture is incorporated, pour the dough on parchment paper and gently roll into a log.
It is time to chill the cookie dough. I prefer to have the dough in the refrigerator for at least 12 hours but four hours is the recommended minimum. The dough would last in the freezer for a couple of months. If you freeze, bring out cookie dough into a refrigerator at least a couple of hours before baking.
When it is time to bake, preheat oven to 300F.
To bake the walnut ginger shortbread, cut the log into 1/4 inch thick coins. Place on a baking tray, preferably lined with parchment paper or a silicone mat.
Bake in the oven for about 20 minutes. The shortbread can be baked longer if you prefer a bit more color on the cookies.
