What a great idea for a pre school activity?
Chocolate pudding cups!
Or you could even do it at home during the summer holidays. It's similar to how you make papier mache masks but forget the paper and glue, use the good stuff instead :D Even when i'm not working in a child care sector i'm always thinking of new ideas and love to stumble across blog posts such as this.
This particular activity is great all round for development especially sensory! I'd perhaps use these at home for pudding but you could also use them for activities at a nursery/school for when any holidays/celebrations coming up and fill them with goodies.
I'd present them in a cupcake box or something similar so it doesn't melt everywhere (Note: hygiene). Also why stop at milk chocolate, you could use white or dark depending on the theme. When it's still wet you could also add edible glitter if you wished. When dry how about the older children having a go at piping chocolate in a contrasting colour?
click photo for recipe and 'how to!'