Cover your receiving tray in wax paper. This will prevent things from sticking
Place chocolate chips and shortening in medium heat-proof bowl. In separate large heat-proof bowl, fill up to 1-inch (2.5 cm) depth with very warm water 100° to 110°F (38° to 45°C). Carefully place bowl with chocolate into bowl with water; water should come halfway up side of chocolate bowl.
Stir chocolate and shortening CONSTANTLY with dry rubber scraper until chocolate and shortening are melted and mixture is smooth. Do NOT get water in bowl with chocolate. (If water cools, replace it with very warm water as directed above; water temperature is important to success). Remove chocolate bowl from inside water bowl.
With fork, dip chilled centers or other dipping items into chocolate mixture, one at a time; gently tap fork on edge of bowl to remove excess chocolate. (For a nice finish on the truffles, invert coated center on prepared tray; swirl small amount of melted chocolate on top to cover fork marks). Let chocolate candies stand until firm. Store candies loosely covered in cool, dry place.