Preheat your oven to 350F degrees. Line baking sheets with parchment paper.
In a mixing bowl, whisk together the flour, baking powder, baking soda, salt, oats, walnuts, and chocolate. Set aside.
Using a mixer (or by hand) beat the butter until fluffy. Beat in the sugar and mix until it is also light and fluffy. Scrape down the sides of the bowl once or twice. Beat in egg and vanilla, mixing until well incorporated, scrape down the sides of the bowl once or twice. Add the flour mixture and stir by hand until the ingredients barely come together into a uniform dough.
Shape 1/2 teaspoon portions of the dough into balls and place two inches apart on your prepared baking sheets. (Just like Heidi specifies in the original recipe, I like these to be very small, a bit more than 1/2 teaspoon of dough. But, after I form the first one, I stop measuring them and just eyeball it.)
Gently flatten each dough ball into a thin, round patty with two fingers and then sprinkle the top of each cookie with a pinch of turbinado sugar. Bake for 5 minutes or until cookies are golden and fragrant. Remove from oven, and cool on a wire rack.