In a large bowl, cream the ½ unsalted butter with the 1 ¼ cups oat flour, ⅓ cup powdered sugar, generous pinch of salt if using, and the 1-2 tablespoons fresh or dried lavender blossoms. The mixture will be crumbly but will come together the longer you beat it.
Grease an 8-inch baking round and line it with parchment paper or use a shortbread mold. Press the dough into the round (I used parchment paper to help me press and smooth it in). Prick the surface all over with a fork. Place in the fridge to chill for 30 minutes.
Preheat the oven to 325℉. When the dough is chilled and firm, place it in the oven and bake for about 30 minutes. Remove from the oven and let cool in the pan for 5 minutes, then gently turn it out onto a rack. Gently flip it over and score the top of the shortbread into 8 slices. Then cut the slices, place on a rack to cool, and transfer to a plate when completely cool.
Notes
What kind of pan? I don't own a shortbread mold (yet?), so I just bake my dough in a greased and lined 8-inch round cake pan. If you have a mold, feel free to use it!
How to cut the cookies? I like to cut the cookies into 8 equal slices, but I equally enjoy gently breaking up the baked round into rustic pieces, and you'll see in these photos.
My dough looks crumbly - help! When you are creaming the butter with the oat flour and powdered sugar, it will seem dry and crumbly at first. This is normal! Keep beating; the dough will start coming together. It's especially important to start with room temp/softened butter so that it blends more easily into the flour.
A finishing touch. Sprinkle the top of the warm shortbread with flaky salt, granulated sugar, or turbinado sugar when it comes out of the oven.
Double the batch. For more cookies, simply make double the recipe and divide it between 2 pans.