S'mores Cookies

INGREDIENTS

• 1/2 cup old-fashioned rolled oats
• 1 cup all-purpose flour, (spooned and leveled)
• 1 cup whole-wheat flour (spooned and leveled)
• 3/4 teaspoon ground cinnamon
• 1/2 teaspoon baking soda
• 1/2 teaspoon salt
• 1 cup (2 sticks) unsalted butter, room temperature
• 3/4 cup light-brown sugar
• 1 large egg
• 8 ounces bittersweet or semisweet chocolate, cut into 30 squares
• 15 large marshmallows, halved horizontally