Preheat your oven to 350°F (175°C) to ensure even baking.
Cream the softened butter and brown sugar together until light and fluffy, about 2-3 minutes.
Add the egg and vanilla extract, mixing until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the sour cream and chopped cashews until smooth.
Scoop rounded tablespoons of cookie dough onto prepared baking sheets, leaving space between each scoop.
Bake for 10-12 minutes or until the edges are lightly golden.
Prepare the icing by whisking together half and half cream, vanilla extract, and confectioner’s sugar until smooth.
Cool the cookies on a wire rack and drizzle with icing, topping each with a cashew half.
