Combine gelatin and cold water; let stand until thick. Place gelatin mixture in top of double boiler and heat until dissolved.
Add glucose and glycerin, mix well. Stir in shortening and just before completely melted, remove from heat and stir in vanilla. Mixture should cool until lukewarm.
Place 4 cups confectioners' sugar in a large bowl. Make a well in the center and using a wooden spoon, stir in the lukewarm gelatin mixture. Mix in sugar and add more a little at a time, until stickiness disappears. Knead in remaining sugar. Knead until the fondant is smooth, pliable and does not stick to your hands. If fondant is too soft, add more sugar; if too stiff, add water (a drop at a time). Use fondant immediately or store in airtight container in fridge. When ready to use, bring to room temperature and knead again until soft.
