Is there a mathematical optimisation technique or algorithm that could, at least in principle, be applied to find optimal ingredient proportions for a given recipe using a minimal number of experiments.
(This is an extended comment, not an answer)
One problem is that you need to make some assumptions about how the quality of the result can depend on the ration of ingredients. For example, suppose we're dealing with a dish with only two ingredients, a priori the response function could be something like:
where there's a sweet spot that makes it taste heavenly, but the proportions have to be just right, otherwise it's so-so. If the peak is narrow, it's unlikely that any systematic-but-mindless search will be able to find the optimum.
For a completely unknown utility function, the best you can hope to find with finitely many tests is a local sort-of-perhaps maximum. And if the only experiment you can do is to compare two recipes at a time to find out which is best, but you have no quantitative notion of how much better (which would probably be too much to ask for), then exploring a high-dimensional parameter space algorithmically is not going to be easy.