Preheat oven to 350 degrees F. Mix chopped cashews, flour, baking powder and baking soda in bowl, and then set aside. In another bowl, beat butter and sugar until light. Beat in egg and vanilla. Mix in sour cream. Mix in flour mixture. Drop heaping Tbsp. of dough onto non-stick or parchment paper-lined cookies sheets, spacing them about 2 inches apart. Flatten cookies out into thick rounds. Insert a whole cashew into the top of each cookie. Bake in the middle of the oven 12-15 minutes, until golden brown.
Note: A 1/3 cup of chocolate chips could be added to the mix if you must have chocolate in your cookies!