I love classic shortbread just as much anyone; but I also love to make shortbread with ground nut flours to take advantage of the flavor of the nuts and make the cookies gluten-free.
Almond flour — the most common nut flour in grocery stores today — is a great canvas for flavor: Here I use clementine or orange zest for brightness and a poppy seed jam filling for a pleasantly bitter tang. Since the proper amount of almond flour is crucial to getting the texture of the cookie just right, I call to pack the flour in the cup like brown sugar, so each cup is the same; if you have a scale, I’ve provided the weight, as well.
Half the dough gets pressed into a pan and par-baked then spread with poppy seed jam and covered in the rest of the dough, which is grated on with a box grater. I learned this technique from a Hungarian shortbread recipe, and it produces small, super-crisp nubbly bits of shortbread on top, good for both variance of texture and to better hold all the blue, silver and white sugar dragées.