Banana-Walnut Chocolate-Chunk Cookies

(From: Martha Stewart’s Cookies, pg 170)

1 cup all-purpose flour
½ cup whole wheat flour
1 teaspoon coarse salt
½ teaspoon baking soda
¾ cup (1 ½ sticks) unsalted, room temperature butter
½ cup granulated sugar
½ cup packed light brown sugar
1 large egg
1 ½ teaspoon pure vanilla extract
½ cup mashed ripe banana (about 1 large banana)
1 cup old-fashioned rolled oats
8 ounces semi-sweet chocolate, coarsely chopped into ¼-inch chucks
(I just used semi-sweet chocolate chips)
½ cup coarsely chopped walnuts (about 2 ounces), toasted
(I did NOT toast the walnuts)

Preheat oven to 375 degrees. Whisk together both flours, salt, and baking soda in a bowl.

Put butter and both sugars into the bowl of an electric mixer fitted with the paddle attachment; mix on medium speed until pale and fluffy. Reduce speed to low. Add egg and vanilla; mix until combined. Mix in banana. Add flour mixture; mix until just combined. Stir in oats and chocolate chunks, and walnuts.

Using a 1 ½ inch ice cream scoop, drop dough onto baking sheets lined with parachment paper, spacing about 2 inches apart. Bake cookies, rotating sheets halfway through, until golden brown and just set, 12 to 13 minutes. Let cool on sheets on wire racks for 5 minutes. Transfer cookies to wire rack; let cool completely.

Cookies can be stored in an airtight container at room temperature for up to 2 days.