Using a mixer, cream butter until creamy. Slowly add in the sugar. Cream until light and fluffy. Add the egg, vanilla and the pumpkin; mix well. Add in the flour, baking powder, salt and cardamom. Stir until combined. Add the white choclate chips. Drop by teaspoon fulls onto a greased cookie sheet. Bake in a 350 degree oven for 10-12 minutes.