A really cool game! The art is great!
A few small things I noticed:
1. The sprite for the cheeseburger seems to be missing, at least for me it's always invisble.
2. The customers never accept the cheeseburger. Whenever an order includes one it's never successful.
3. One time a customer wanted a "tomato and cheese toastie", I made a "cheese and tomato toastie" and they were not happy with that.
Regarding points 2 and 3:
Do you do a string comparison to check if the right things were made?
That would explain point 3 and also point 2 because what I can make is a "cheese burger" and what the customers want is a "cheesebruger" (notice the missing whitespace and the typo).
But all in all this was a very enjoyable game.
And because there is no time limit you can experiment to your hearts content to find the correct recipies.
A very good job overall!