- 2 sticks of butter, slightly warmed (to 55°F)
- 3/4 cup sugar
- 1/2 cup light brown sugar
- 1 egg
- 1/2 teaspoon vanilla extract
- 1 1/4 cups flour
- 1/2 teaspoons baking powder
- 1/2 teaspoons baking soda
- 1 teaspoon kosher salt
- 1 1/2 cups rolled oats
- Large-grained sea salt, such as Maldon or Fleur de Sel
Preheat oven to 350°F and adjust rack to middle position. Cream butter and sugars in stand mixer fitted with paddle attachment on medium-high speed until light and fluffy, scraping down sides with rubber spatula as necessary, about 2 minutes. Add egg and vanilla and mix on medium speed until incorporated, about 30 seconds.
Add flour, baking powder, baking soda, salt, and oats to large bowl and whisk to combine. With mixer running on low, slowly add flour mixer and mix until just combined, about 30 seconds.
Using moist fingers or #30 ice-cream scoop, form into 24 to 30 balls, about two tablespoons each and divide onto three parchment-lined cookie sheets, leaving about two inches of space between balls.
Working with one batch at a time, bake until cookies are golden brown and set around the edges (centers will still be soft), about 15 minutes, removing cookies from oven after 8 minutes to sprinkle with sea salt to taste (about 1/4 to 1/2 teaspoon per cookie), and rotating baking sheet. Allow to cool completely before serving.