Heat the oven to 350°F with racks in the upper and lower thirds. Parchment-line two light-colored sheet pans.
Whisk white whole-wheat flour, oat flour, baking soda and salt for 20 seconds.
Whisk cooled melted butter, brown sugar and maple syrup until glossy with no dry sugar pockets.
Whisk in egg and vanilla for about 30 seconds until slightly thickened and emulsified.
Fold in the flour mixture, then chocolate chips, stopping as soon as no dry streaks remain.
Cover and refrigerate 30 minutes, until the dough holds a rounded scoop without flowing.
Divide into 18 level 2-tablespoon portions, about 32 grams each, and press into half-inch disks 2 1/2 inches apart.
Bake 9 to 12 minutes, rotating and switching racks around minute 6, until edges are light golden and centers are matte but soft.
Add optional flaky salt, cool on pans 8 minutes and transfer to a wire rack.
