Making it easier:

Have a set of pictures of ingredients which are appropriate for what you are making, and some other ingredients. Get the children to choose the appropriate ingredients.

Even easier:

Have a set of pictures for the ingredients, and some further pictures which aren't food (e.g. pictures of furniture, clothes). Help the child to choose those which are food items.

Harder:

Get the children to draw and/or write down the ingredients themselves.

On subsequent occasions, you can pretend that you have a really bad memory, and you need the children to help you to remember what to take. If they don't remember everything, you can look a bit confused, and say something like "I'm sure we need to take something else...".

You could also use ideas based on the comments in "Deciding on the ingredients".

If the children are familiar with cooking this item, but they sequenced the pictures for doing the activity incorrectly at the beginning, you don't necessarily have to correct them straight away - you can correct it at the point when it becomes a problem - e.g. if you get to the putting the pizza in the oven bit before you've put the sauce and toppings on (look very confused!).

Sketches for the sequence - these do not need to be accurate at all - they will be useful for this activity no matter what level of drawing ability you have. The children can also help with this.

You can incorporate a number of maths concepts into the activities, for example: "full", "empty", "more", "less", "hot", "cold".

Safety. Clearly you will need to manage any dangerous aspects of the cooking process as appropriate for the children you are working with (e.g. use of knives, the cooker).