Grease cookie sheet and insides of two or more heart-shaped cookie cutters 4 inches long and 2 inches deep. Place cutters on cookie sheet, set aside.
In large bowl, combine cereal, chocolate chips, marshmallows, candied cherries and pecans, set aside.
In small heavy saucepan over very low heat, stir white chocolate and shortening until melted and smooth. Remove from heat, cool slightly. Pour chocolate mixture over mixture in bowl, stir gently to coat completely.
Using greased fingers, press about 2/3 cup mixture firmly and evenly into each prepared cutter on cookie sheet to thickness of up to 3/4 inch. Refrigerate 30 minutes until firm. Depending on number of molds available, you may have to work in batches. Keep unused mixture at room temperature between batches.
To unmold: Run wide metal spatula under cutters to loosen from cookie sheet. Using fingers, gently push each sweetheart free of the cutter.