Mini Hazelnut Maple Sandwich Cookies - Diamond Nuts

Ingredients

• Cookies:
• 1/2 cup unsalted butter, room temperature (1 stick = 1/2 cup)
• 1/2 cup light-brown sugar
• 1 large egg yolk
• 1/3 cup maple syrup (preferably grade A)
• 1 1/4 cups all-purpose flour, plus more for surface
• 3/4 cup Diamond of California® Walnuts, finely diced
• 1/4 teaspoon salt
• Filling:
• 1/4 cup unsalted butter, softened (1/2 stick = 1/4 cup)
• 2 cups powdered sugar
• 3 tbsp maple syrup
• 1 tsp maple extract