For an even chewier texture, substitute 1/2 cup hazelnut or almond flour for 1/2 cup all-purpose flour.
3/4 cup uncooked regular oats
1/4 cup butter, softened
3/4 cup firmly packed light brown sugar
1/2 cup granulated sugar
2 large eggs
1 teaspoon vanilla extract
1 3/4 cups all-purpose flour
1/2 teaspoon baking soda
1/2 teaspoon salt
1/4 teaspoon baking powder
3 (4-oz.) bittersweet chocolate baking bars, coarsely chopped and divided
How to Make It
Preheat oven to 400°. Bake oats in a 9-inch pie plate 10 to 12 minutes or until toasted and fragrant, stirring halfway through. Cool completely on a wire rack (about 30 minutes). Process oats in a blender or food processor 1 minute or until finely ground.
Beat butter and sugars at medium speed with a heavy-duty electric stand mixer until fluffy. Add eggs and vanilla, beating just until blended.
Stir together flour, next 3 ingredients, and ground oats in a small bowl; gradually add to butter mixture, beating just until blended after each addition. Fold in 2 1/4 cups chopped chocolate (about 2 bars) just until combined. Cover dough, and chill 8 to 12 hours.
Preheat oven to 350°. Drop dough by heaping tablespoonfuls onto parchment paper-lined baking sheets (about 6 per sheet).
Bake at 350° for 10 to 12 minutes or until golden brown; press remaining chocolate into cookies. Remove from baking sheets to wire racks; cool completely (about 15 minutes).