In a small saucepan, brown the butter. Scrape browned butter and all its bits into a small bowl. Let cool slightly then refrigerate until it is soft set.
Preheat oven to 375°F. For crunchier cookies or cookies that bake more evenly throughout, preheat to 325°F.
In the bowl of a stand mixer with the whisk attached, combine your set browned butter (89 grams) and both sugars and beat for 2 minutes. It will smell really good!
Remove the bowl from the stand and add the egg, vanilla, baking soda and salt. Return to mixer stand and beat for another two-three minutes, scraping sides of the bowl often.
Add the oat flour and flour and stir until fully blended.
Add chocolate chips, walnuts and orange zest (if using).
Using a small cookie scoop (1 tablespoon) scoop out balls of dough. You should get about 28. For smaller Famous Amos size cookies, make the dough balls a little over half that size or about 10 grams each.
Arrange the dough balls 2 inches apart on an ungreased baking sheet. For the larger cookies, bake for 8 minutes at 375. Rap the pan on the counter and bake for another 2-4 minutes or until the edges are lightly browned.
Alternatively, you can bake the cookies at 325 for 14-18 minutes. The cookies should spread a little without you having to press them down, but if you want a more even crunchy bake, press the rounded tops flat.
Let the cookies cool completely before serving. They should crisp as they cool.