makes about 28 cookies
1 cup unsalted butter, chopped
2 1/2 cups gluten-free AP flour
1 1/2 cups gluten-free oat flour
3/4 cup gluten-free rolled oats
1 1/4 teaspoons baking powder
1 teaspoon baking soda
1 1/2 teaspoons kosher salt
1 1/2 cups light brown sugar, firmly packed
1/2 cup granulated sugar
2 teaspoons vanilla extract
12 ounces, semi or bittersweet chocolate, chopped (or chips)
1/2 cup hazelnuts, roughly chopped
flaky salt, to finish
Preheat the oven to 360°F. Line 2 rimmed baking sheets with parchment paper.
Melt the butter in a heavy bottomed saucepan over the lowest heat possible, stirring occasionally. Make sure the butter does not sizzle or bubble which means it's losing moisture.
In a bowl, whisk together the flours, oats, baking powder, baking soda, and salt. Set aside. Pour the melted butter into a large bowl and whisk in the sugars until smooth. Add the eggs, one at a time, whisking until just combined. Stir in the vanilla. Use a wooden spoon or silicone spatula to stir in the dry ingredients until barely blended. When things are still looking a bit floury, stir in the chocolate and hazelnuts until all of the ingredients are just combined.
Roll the dough into balls, about 3 tablespoons each, and arrange them on the prepared pans, leaving 3 inches between each cookie. (At this point you can refrigerate the dough, loosely covered, overnight.)
To bake, sprinkle each cookie with a bit of sea salt and bake until the tops are cracked and lightly golden, 12-14 minutes, rotating the pan halfway through. Cool on the pan for 2 minutes, the move to a wire rack to cool completely.