Step 1

Preheat oven to 350 degrees F.

Step 2

In a large mixing bowl, cream butter, 1 cup of sugar and the powdered sugar. Add vegetable oil and eggs and mix well.

Step 3

In a separate bowl, combine cornstarch, baking soda, cream of tarter, salt, cocoa and flour and stir to mix..

Step 4

Add to wet ingredients to the dry ingredients and mix until well incorporated.

Step 5

Roll dough into 1 inch balls and place on cookie sheet.

Step 6

On a large plate, spread ¼ c of sugar. Find a smooth bottomed glass and press it into the sugar to coat the bottom of the glass in sugar. Then press the sugar-coated-glass into the cookie dough balls and lightly press down until your dough begins to flatten and the edges around the glass begin to split.

Step 7

Bake at 350 degrees F for 8 minutes. Cool cookies on a cooling rack and then put them in the fridge until you are ready to frost them.

Step 8

Combine butter, powdered sugar, cocoa and heavy cream in a medium mixing bowl and beat until smooth. Add vanilla and mix until smooth.

Step 9

Frost cooled cookies.