I originally did this activity for a class that I taught twice in a day, but it would work equally well on sequential days.

Equipment
Recipe cards labelled A, B, C, D
Microwave or friendly food tech teacher who will lend you their room
Rice Crispies (or Cornflakes)
Chocolate
Bowls & spoons
Oven glove
Cake cases

Aim
If you haven’t guessed from the equipment list, you are making chocolate rice crispie cakes to investigate ratio.

Before you start
You need to have at least 4 different recipe cards. Two of them should have the same ratio of chocolate to cereal, but in different quantities. I had one as double the other. The other two should have common errors eg adding rather than multiplying to increase.

Practical
The messy part.

Make the rice crispie cakes and leave them to set. You should make sure each set of cakes is labelled with the recipe letter.

Discussion
This is the fun part. Taste testing in the second lesson – they will be keen to get started.

Each pupil tries each recipe and comments on how they taste. Depending on your recipes, one should be too dry, one should be too chocolatey* and two should be identical. You can then look at the recipes to explain this by comparing quantities and introducing ratio.

*Some will say you cannot have too much chocolate, but if you use Mars bars the high sugar content means they go rock hard if there is not enough cereal. So hard in fact that two boys decided to eat a whole cake each because no one else wanted them and they were quiet for more than ten minutes!

You’re being watched…
I first did this activity 10 years ago when I knew I was being watched by my Head of Department in the tasting/discussion section. The class were a bouncy low ability Y9 group.

They loved it, my HoD loved it and it’s never let me down as a lesson concept since.