3 cups old-fashioned oats
1 cup all-purpose flour
1 teaspoon baking soda
2 teaspoons ground cinnamon
1/8 teaspoon ground nutmeg
1/4 tsp salt
2 sticks (8 ounces) unsalted butter, at room temperature
1 cup peanut butter
1 cup sugar
1 cup (packed) light brown sugar
2 large eggs
1 teaspoon pure vanilla extract
9 ounces bittersweet chocolate, chopped into chunks, or 1 1/2 cups store-bought chocolate chips or chunks (I chose a different direction; I went with 3/4 cup bittersweet chocolate chips and 3/4 cup semi-sweet chocolate chips to ensure the bittersweet chocolate did not overwhelm)
Position the racks to divide the oven into thirds and preheat the oven to 350°. Line two baking sheets with parchment or silicone mats.
Whisk together the oats, flour, baking soda, nutmeg, cinnamon and salt. Working with a stand mixer fitted with a paddle attachment, or with a hand mixer in a large bowl, beat the butter, peanut butter, sugar and brown sugar on medium speed until smooth and creamy. Add the eggs one at a time, beating for 1 minute after each addition, then beat in the vanilla. Reduce the mixer speed to low and slowly add the dry ingredients, beating only until blended. Mix in the chocolate chips.
If you have the time, cover and chill the dough for about 2 hours or for up to one day. (Chilling the dough will give you more evenly shaped cookies.) I couldn’t wait that long but did chill the dough for about an hour, they turned out great.If the dough is not chilled, drop rounded tablespoonfuls 2 inches apart onto the baking sheets.
If the dough is chilled, scoop up rounded tablespoons, roll the balls between your palms and place them 2 inches apart on the sheets. Press the chilled balls gently with the heel of your hand until they are about 1/2 inch thick.
Bake for 13 to 15 minutes, rotating the sheets from top to bottom and front to back after 7 minutes. The cookies should be golden and just firm around the edges. Lift the cookies onto cooling racks with a wide metal spatula – they’ll firm as they cool.
Make sure you wait for the baking sheets to cool completely before making the next batch. And I used parchment paper, which I turned over to use the unused side for the second batch.