Speaking as both a writer and as a home cook, it is a rule of thumb not to accept substitutes whenever one prepares something that is meant to be enjoyed by both one’s self and others. However, for one reason or another, there are cases wherein the substitution of one or two ingredients makes a profound difference that leads to an end-result that is far and away lots better than the original.
The closest analogy I can see is in film, specifically with regard to X-Men: First Class. If at first people balked at how screen stalwarts Sir Patrick Stewart and Sir Ian McKellen were replaced by the much, much younger James McAvoy and Michael Fassbender as Charles Xavier and Magneto. The substitution is one of the reasons why the flick is currently so successful – the fresh blood, the dynamism, and the well-considered chemistry all come into play and play very well. And it doesn’t hurt that both young gents look mighty pleasant.
As far as food is concerned, the act of substitution – especially in primary ingredients – is far trickier. Consider the many dishes which have been made suitable for vegetarians or, worse, vegans: chunks of gluten paste, konnyaku (devil’s tongue jelly), or tofu take the place of meat, fowl, and fish – and often with disastrous results.
One particularly fiddly dish to play around with is sisig, an artery-clogging concoction of finely minced pork offal – usually the face, ears, snout, and brain – wok-fried with finely chopped onions, a touch of vinegar, eggs, chilies, and ground black pepper. Richly flavored with an excellent variety of textures, many well-meaning “healthy” chefs have tried to replicate this Kapampangan specialty with varying mixtures of tofu and gluten. All of which, I regret to say, have done nothing for me save turn my face green from disgust.
That said, my favorite non-pork sisig is not really vegetarian as it’s made with fish! And it’s a rather tasty one, too. A combination of grilled yellowfin tuna and bangus (milkfish) fillets are roughly diced, sauteed with spring and red onions, some ginger, chilies, and copious amounts of freshly-ground black pepper, then plated up with a squeeze of kalamansi and more fresh siling labuyo (bird’s-eye chili).
Unlike classic sisig which serves more as bar chow, fish sisig is perfect as a meal when paired with rice and a light salad of steamed kamote (sweet potato) tops mixed with diced tomatoes and a crushed salted egg quarter. Certainly not as fatty or as greasy as the calorific original, but nevertheless tasty and satisfying.