Preheat oven to 350 degrees.
Wet ingredients: In a medium bowl, beat softened butter and dark brown sugar on with a whisk or using an electric mixer. Then, add egg and vanilla extract.
Dry ingredients: In a large bowl, mix together rolled oats, white whole wheat flour, ground flax seed, baking powder and salt.
Combine butter and brown sugar mixture with the oats and flour mixture until just combined. Do not overmix.
Fold in chocolate chips.
Line two baking sheet with parchment paper or a silicone baking mat. Using a cookie scoop or spoon, scoop dough onto each baking sheet. Dough should make about 20 cookies, but you can make them bigger or smaller if you prefer. They don't spread very much on the cookie sheet so I prefer to shape into a cookie shape.
Bake for about 8 minutes until top is slightly golden brown and then cool on a wire rack. The cookies will be very soft but will continue to set as they cool.