1Heat oven to 375°F. Beat granulated sugar, butter, vanilla, chocolate and egg in large bowl with electric mixer on medium speed, or mix with spoon. Stir in flour and salt.
2Shape dough by tablespoonfuls into balls. Place about 3 inches apart on ungreased cookie sheet. Press thumb or end of wooden spoon into center of each cookie to make indentation, but do not press all the way through.
3Bake 8 to 10 minutes or until firm. Quickly remake indentations with end of wooden spoon if necessary. Immediately remove from cookie sheet to wire rack. Cool completely, about 30 minutes.
4Mix peanut butter and powdered sugar. Fill each thumbprint with about 1 teaspoon peanut butter mixture or jelly. Sprinkle with peanut brittle.