2 cups old-fashioned rolled oats
2 cups all-purpose flour
1 teaspoon baking powder
1 teaspoon baking soda
1/2 teaspoon salt
1 cup (2 sticks) unsalted butter, at room temperature
3/4 cup light brown sugar, packed
1/2 cup granulated sugar
2 tablespoons light corn syrup
2 large eggs
2 teaspoons vanilla extract
12 ounces semisweet chocolate chips, or 12 ounces top-quality bittersweet or semisweet chocolate, chopped into small chunks
3-1/2 to 4 ounces top-quality milk chocolate, finely chopped or coarsely grated
1 cup chopped walnuts or pecans, toasted (optional)
Recipe
Heat the oven to 350 degrees F. Line several baking sheets with parchment paper or silicon baking mats.
In a food processor or blender, grind the oats to a very fine powder. (If using a blender, stop the motor and stir the oats several times.) In a large bowl, thoroughly stir together the oats, flour, baking powder, baking soda, and salt; set aside. In another large bowl, with an electric mixer on medium speed, beat the butter until light and fluffy. Add the brown sugar, sugar, and corn syrup and beat until well blended and fluffy. Add the eggs and vanilla and beat until evenly incorporated. Beat in about half of the flour mixture. Beat or stir in the chocolate morsels, chopped milk chocolate, walnuts or pecans (if using), and remaining flour mixture until evenly incorporated. Let stand for 5 to 10 minutes, or until the dough firms up just slightly.
Divide the dough into quarters. Divide each quarter into 5 or 6 equal portions. Shape them into balls with lightly greased hands. Place on the baking sheets, spacing about 3 inches apart. Using your hands, pat down the balls to 1 inch thick.
Bake the cookies, one sheet at time, in the upper third of the oven for 9 to 12 minutes, or until tinged with brown and just beginning to firm up in the centers; for very moist cookies, be careful not to overbake. Reverse the sheet front to back halfway through baking to ensure even browning. Transfer the sheet to a wire rack and let stand until the cookies firm up slightly, 3 to 4 minutes. Using a spatula, transfer the cookies to wire racks. Let stand until completely cooled.
Store in an airtight container for up to 1 week or freeze for up to 1 month.
Note: Sometimes I leave out the milk chocolate and add more dark chocolate instead. And when I make these cookies, I refrigerate the dough overnight and then shape rounded teaspoonfuls into balls. This makes smaller, more compact cookies, which I prefer. For thinner, slightly crisper cookies, follow the directions above.