Melt chocolate and condensed milk in slow cooker
Stir with a metal spoon every 10 minutes, cooking on high for 1hr
When a smooth even mixture has formed, add 1/2 packet of jelly crystals and stir
Pour into lined baking dish
Whilst mixture is still warm, add a few drops of food dye and swirl with a toothpick
Place in fridge to set then cut into desired shapes