1. Preheat oven to 350°F. Line a baking sheet with parchment paper or greased foil. Set aside.
2. In a medium bowl, stir together all the dry ingredients: flour, oats, baking powder, cinnamon and salt. Set aside.
3. In a large bowl, whisk together all the wet ingredients: melted (but not hot) butter, sugar, egg and vanilla. Whisk until well-mixed.
4. Add the dry mixture to the wet mixture. Whisk as long as you can. Switch to stirring and folding with a rubber spatula until no flour patches remain. Fold in add-ins.
5. Cover bowl and chill in the freezer for about 20 minutes, until firm throughout. If necessary, allow to thaw at room temperature just until it’s soft enough to scoop, but still very firm and chilled.
6. Using a medium cookie scoop, scoop and drop cookie dough balls onto the prepared cookie sheet, evenly spaced apart. Cookies will spread. For large, wide cookies, flatten the dough no more than half-way. Otherwise, bake cookies in balls.
7. Bake for 14-16 minutes, until deep golden on the bottom and golden on the edges—you can also take them out before the edges are golden—this will yield a softer cookie. Mine took 16 minutes (I like them crispy!).
8. Allow cookies to cool on the cookie sheet for about 10 minutes (on a cooling rack). Using a heatproof spatula, lift cookies off the sheet and transfer directly onto a cooling rack to cool completely before storing. Storing instructions below. Enjoy!

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