In a large mixing bowl, combine butter, vegetable oil, white sugar, brown sugar, egg, pumpkin, and vanilla. You could substitute another ½ cup of butter in place of the ½ cup of vegetable oil.
In a medium bowl, mix together the flour, cornstarch, cream of tartar, baking soda, baking powder and salt. Add the cinnamon, ginger, nutmeg and allspice and mix until well combined.
Slowly add dry ingredients to the wed ingredients, combining well after each addition.
Dough can be chilled to make it easier to work with, or you can bake them right away.
When ready to bake, preheat the oven to 350 degrees.
Roll the dough into 1 inch diameter balls, then roll each ball in the cinnamon and sugar mixture before placing on a cookie sheet, 2 inches apart.
Bake for 12-14 minutes or until slightly browned. Makes about 4 dozen cookies.