Adjust oven rack to middle position, and preheat to 350° F. Sift flour into medium bowl, then add oat flour, rolled oats, steel-cut oats, and toasted nuts. (Stella says that if you put this mixture in an airtight container, it'll keep for 2 months at room temperature!)
Combine the butter, brown sugar, white sugar, salt, baking soda, cinnamon, and vanilla in the bowl of a stand mixer with the paddle attachment. Mix on low to get all the ingredients moist, then increase to medium and beat for around 30 seconds. With the mixer running, crack the egg into the mixture and continue mixing until smooth. Reduce the speed to low, and add the dry ingredient mixture, and mix to form a stiff dough.
Divide the dough in half, and place each half in a bowl. In one half, fold in the chocolate chips. In the other, fold in the raisins. (Alternatively, you can just go all in on one or the other, and add a full cup to the dough.)
Arrange 32 portions of dough (about 2 tablespoons each) onto parchment-lined aluminum baking sheets, leaving 2 inches between them. Flatten into 1/2 inch discs. Bake until puffed and light gold around the edges, but pale and steamy in the middle, about 12 minutes. Cool on baking sheet until set, about 5 minutes.