Chocolate Hazelnut Cookie Sandwiches - DeLallo

Ingredients

• 2 1/2 sticks unsalted butter (1/2 stick cold and 2 sticks at room temperature)
• 1/2 cup rolled oats
• 1 3/4 cup Nutella, or chocolate-hazelnut spread
• 1/2 cup dark brown sugar
• 1/2 cup sugar
• 2 cups all-purpose flour
• 2 teaspoons baking soda
• 2 teaspoons kosher salt
• 1/4 cup coarse, decorating sugar (optional)