I made a sponge cake using a recipe from an old cookbook and at one point it told me to melt and boil butter and pour the boiling butter into beaten egg-whites, let sit for a minute and then mix gently. This procedure puzzles me. Why should I pour in the butter while hot? If you want the whole thing, here goes (no measures, 'cause it's in Polish and uses Polish measures, where "one cup" is not what you would call "one cup"):  beat egg whites with powdered sugar until stiff pour in melted and boiling butter (or shortening), mix gently after one minute and let sit until it cools. Start mixing again and add egg yolks one by one, then lemon juice and finally flour mixed with baking powder. Mix a bit more. Bake for at least 50 minutes at 160 degrees C  The batter looks fine, it's baking nicely, but the long time is also strange for me, most sponge cakes that I made require just 20-25 minutes of baking. I skimmed the book, but didn't notice any other sponge cake recipe with this approach. 
There's a proposal to get allergens into Unicode as emoji.  Unfortunately, this might only work for digital usage, as you could then compare code-points, as in the printed version, different fonts might render the symbols dramatically differently.  Even if there were standard forms for the new code-points, the proposal recycles a few existing characters (cow, octopus, chicken, apple, orange, etc.), so it's more likely that there would already be significant variation.  (and this would only cover allergies and intolerances due to ingredients, not restrictions based on processing (eg, Halal, raw vegan, fruitarian)) 