- Whisk oats, flour, baking powder, cinnamon, and kosher salt together in a large bowl.
- Combine honey, applesauce, butter, egg, and vanilla extract in a medium bowl. Whisk until blended. Pour into the bowl with the flour mixture; stir until just combined. Fold chocolate chips and walnuts into the batter.
- Place batter in the refrigerator and let chill at least 30 minutes or up to 3 days.
- When ready to bake, preheat the oven to 350 degrees F (175 degrees C) and place a rack in the center. Line a large, rimmed baking sheet with parchment paper or a silicone baking sheet.
- Remove chilled dough from the refrigerator. Let sit for 5 to 10 minutes if very stiff.
- Drop dough onto the prepared baking sheet in 1 1/2-inch balls using a cookie scoop or spoon, leaving 1 inch of space around each. Gently flatten each cookie with your fingers to 3/4-inch thick.
- Bake in the preheated oven until golden, firm around the edges, and set on top, 9 to 10 minutes.