Heat oven to 375°F. Spray cookie sheets with cooking spray. Melt 6 oz white chocolate as directed on package. Cool slightly, about 5 minutes.
In large bowl, beat brown sugar and butter with electric mixer on medium speed until light and fluffy. Beat in vanilla and egg until well blended. Beat in melted chocolate until well blended. On low speed, beat in flour, baking soda and salt until well blended.
Shape dough into 1-inch balls. Place 2 inches apart on cookie sheets. With thumb or handle of wooden spoon, make indentation in center of each cookie. Spoon jelly into small bowl; stir until smooth. Place 1/2 teaspoon jelly in each indentation. (Cookies will look full.)
Bake 5 to 8 minutes or until edges are very light golden brown (do not overbake). Cool 1 minute; remove from cookie sheets to cooling rack. Cool completely, about 10 minutes.
Melt 4 oz white chocolate with shortening as directed on package. Cool slightly, about 5 minutes. Place mixture in resealable food-storage plastic bag; seal bag. Cut small tip from bottom corner of bag. Squeeze bag to drizzle glaze over cookies.