California Walnut Sugar Cookies – DelicioUS!

Ingredients

• 260 g flour
• 170 g California Walnuts, very finely chopped
• 1/2 tsp baking powder
• 1/4 tsp salt
• 115 g butter, at room temperature
• 135 g vegetable shortening, room temperature
• 250 g granulated sugar
• 1 egg, at room temperature
• 1 1/2 tsp vanilla extract
• 2 egg whites
• 1/2 tsp vanilla extract
• 455 g powdered sugar
• decorative sugar (optional)