In a 2 qt. saucepan cook together sugar, pumpkin, spice, cornstarch and milk, stirring frequently until mixture reaches 234 degrees on a candy thermometer or a small amount forms a soft ball in a little cold water. Add vanilla and cool in a pan of ice water to 110 degrees. Beat until fudge loses its gloss. Pour into a lightly buttered 8 x 8 x 2 inch pan and cool. Score and cut when almost cold. Store in a wax paper lined metal can. Will keep for several weeks. If nuts are desired, mix in 1 cup of broken walnuts when the vanilla is added.