Heat oven to 350°F. In large bowl, beat sugar, butter, vanilla and egg with electric mixer on medium speed, or mix with spoon, until well blended. Stir in flour, cocoa and salt until dough forms.
Shape dough by rounded teaspoonfuls into 1-inch balls. On ungreased cookie sheets, place balls about 2 inches apart. Press thumb or end of wooden spoon into center of each cookie, but do not press all the way to the cookie sheet.
Bake 7 to 11 minutes or until edges are firm. If necessary, quickly remake indentations with end of wooden spoon. Immediately remove from cookie sheets to cooling racks. Cool completely, about 30 minutes.
Meanwhile, in 1-quart saucepan, heat whipping cream over medium heat, stirring occasionally, until steaming.
Remove from heat; stir in chocolate chips until melted. Cool about 10 minutes or until thickened.
Spoon rounded 1/2 teaspoon filling into indentation in each cookie. Top with decors.
