For the hot chocolate bombs:Using a double boiler or microwave (in 30 second increments), melt the chocolate chips until smooth.Evenly divide the chocolate amongst two medium size 6 semi sphere silicone mold trays. Using a spoon, smooth the chocolate up the sides of each mold until evenly coated.Refrigerate for a minimum of 30 minutes to allow chocolate to firm. If any weak areas appear, brush with additional chocolate.Carefully removed the chocolate from the molds. Evenly divide the hot chocolate powder, crushed candy cane and marshmallows amongst half of the molds.Press the remaining molds against a hot plate (microwaved for 15 to 20 seconds). Matching the seams to the filled mold, press together to seal. Run edges with a warm spoon to smooth out any imperfections.Drizzle with milk chocolate and sprinkle with additional crushed candy cane. Refrigerate until ready to use.For the hot chocolate:Place a hot chocolate bomb in desired mug.Heat together the eggnog and milk using a saucepan or frother.Pour mixture over the hot chocolate bomb and stir.Top with whipped cream if desired!