Ingredients
3 1/4 cups (445 g) homemade grain-free flour blend (see recipe below), or preferred gluten-free all-purpose flour
1/4 cup (35 g) cornstarch
1 1/4 teaspoons (5 g) baking powder
1 teaspoon (7 g) Kosher salt, plus more for sprinkling
1 teaspoon (6 g) baking soda
2 sticks (8 ounces) unsalted butter, at room temperature
1 cup (212 grams) granulated sugar
1 cup packed (200 grams) light brown sugar
2 large eggs, at room temperature
2 teaspoons pure vanilla extract
1 pound best-quality bittersweet chocolate (50-75% cacao content), chopped (about 3 1/2 cups)
1 cup tapioca flour, spooned and leveled
1 cup arrowroot flour, spooned and leveled
1 cup coconut flour, spooned and leveled
1 cup almond flour, spooned and leveled
Instructions

    For the cookies:

  1. Whisk together dry ingredients in a medium bowl: flour, cornstarch, baking powder, salt, and baking soda; set aside. In the bowl of an electric mixer, beat the sugars with butter until very light and fluffy, doubled in volume, and no longer sandy to the touch, pausing to scrape down the sides of the bowl once (about 4 minutes). With mixer on medium speed, beat in eggs one at a time until combined; add vanilla. With the mixer on low, add flour mixture a heaping spoonful at a time, pausing to let each one incorporate. Stir in chopped chocolate by hand.
  2. Use a 1-ounce cookie scoop (or a slightly heaping tablespoon measure) to scoop portions of dough into about 1 1/2-inch balls onto a parchment-lined sheet (they can touch). Repeat with remaining dough. Cover sheet and chill 1 hour. (The sheet can also be transferred to the freezer at this point; once the dough portions are frozen, they can be broken apart and transferred to a zippered freezer bag and stored up to 3 months and baked directly from frozen.)
  3. To bake, preheat oven to 350°F with racks dividing the oven into upper and lower thirds. Arrange dough portions onto parchment or Silpat-lined sheets a few inches apart (12 per sheet). Sprinkle cookies with additional kosher salt. Bake cookies, rotating pans halfway through, until no longer wet-looking and very lightly golden brown around edges (12 to 14 minutes). Rest cookies on sheets for 5 minutes; use a thin spatula to transfer cookies to a wire rack to cool completely.

    For the homemade grain-free flour blend:

  1. Whisk together flours in a medium bowl. To store, transfer flour mixture to an airtight container and place away from heat for up to 3 months.