Chocolate Crinkle Cookies

Many thanks to Lee for this recipe. These cookies are irresistible.
 
2 cups sugar
3/4 cup vegetable oil
3/4 cup cocoa
4 eggs
2 teaspoons vanilla*
2 1/3 cup flour
2 teaspoons baking powder
1/2 teaspoon salt
Powdered sugar

Mix the sugar and oil together. Add the cocoa and blend well. Beat in the eggs and vanilla.
Mix the flour, baking powder and salt thoroughly. (Don't skip this step. It really helps.) Add dry ingredients to the cocoa mix, blending thoroughly.
Cover the dough and refrigerate for 6 hours. (If you really need the cookies sooner, put the dough in the freezer for 30-45 minutes.)
Heat oven to 350o. Grease cookie sheets. Shape dough into balls an inch to an inch and a half in diameter, roll these in powdered sugar until they are well coated, and place them 2 inches apart on the cookie sheets. (The dough will be sticky, but coating fingers with powdered sugar before rolling a ball helps.)
Bake 12 to 14 minutes, or until a dent in a cookie barely remains when touched. (12 minutes in a preheated oven is perfect for soft, chewy cookies. Don't overcook them; that changes the taste and texture. They just aren't as good hard as they are soft.)
This recipe makes 4 dozen cookies if you are rolling inch-and-a-half balls of dough.

*If at all possible, use Mexican vanilla. It improves any recipe calling for vanilla tremendously.