Ingredients:

• 1 cup all-purpose flour
• 1/2 cup whole-wheat flour
• 1 tsp coarse salt
• 1/2 tsp baking soda
• 3/4 cup (1.5 sticks) unsalted butter, softened
• 1/2 cup granulated sugar
• 1/2 cup packed light-brown sugar
• 1 large egg
• 1.5 tsp pure vanilla extract
• 1/2 cup mashed ripe banana (about 1 large)
• 1 cup old-fashioned rolled oats
• 8 oz semisweet chocolate, coarsely chopped into 1/4-inch chunks
• 1/2 cup coarsely chopped walnuts (about 2 oz), toasted

Directions:

1. Preheat oven to 375. Whisk together flours, salt, and baking soda in a small bowl; set aside. Put butter and sugars into the bowl of an electric mixer fitted with teh 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, chocolate chunks, and walnuts.
2. Using a 1.5-inch ice cream scoop, drop dough onto baking sheets lined with parchment 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 5 minutes. Transfer cookies to wire racks; let cool completely. Cookies can be stored in airtight containers up to 2 days.