Before baking, preheat oven to 350°F / 180°C / Gas Mark 4
Note: Refrigerate dough 1-2 hours or until firm enough to handle.

In a large bowl, beat butter, sugar, 2 eggs, milk and 1 teaspoon of vanilla until well blended.

Stir together flour, cocoa and salt; add to butter mix, mixing until well blended. Refrigerate dough 1-2 hours.

Lightly grease cookie sheets. Shape dough into 1 inch balls and place on cookie sheets. Press thumb gently in center of each cookie.

Bake for 10-12 minutes or until set. Cool slightly; remove from cookie sheets to wire rack. Cool completely.

Green and Orange Frosting:
In a small bowl, combine powdered sugar, softened butter, 2 tablespoons of milk and 1 teaspoon of vanilla. Beat on high until smooth. Remove 2 tablespoons and tint this with green food color; set aside.

Add freshly grated orange peel to remaining icing and use red and yellow food coloring to make orange. Spoon about 1/4 tsp orange frosting in each thumbprint cookie. Decorate with green filling to look like stem of a pumpkin.

To make Ghost Cookies:
Make icing and omit food coloring and orange peel. Decorate cookies to look like ghosts.