makes 100 mini cookies
Mix the usual cookie way: cream butter and sugars. Add eggs and vanilla. In separate bowl, whisk flours, oat bran and leavening—this step is important with oat flour, as it tends to clump. Add flour mixture to creamed butter and sugar mixture, mix to combine. Stir in chocolate chips.
Get out your plastic wrap. Aim to make about 3 logs with your dough. The dough is somewhat loose, so when you put some on the plastic wrap use the plastic to help you squeeze and roll the dough into a 10-12 inch long, couple inch in diameter, log. (It doesn't have to be exact, you're just getting yourself set up for easy "slice and bake" later.) Transfer dough logs into the refrigerator.
When you want to bake the cookies, preheat oven to 375° F. Line a cookie sheet pan with a silpat liner or with a sheet of baking parchment paper. Unwrap chilled dough log and slice every inch or so, then quarter each slice to make small dough pieces. Put the dough pieces on the lined sheet pan, approximately 20 per pan. (Put remaining dough back in the refrigerator until its turn to bake.)
Bake for 6 minutes or until cookies are lightly browned. Let cool on sheet pan for 5 minutes, then move cookies to a cooling rack.