India, Oct. 1 -- It's the early 17th century in Goa. Behind the soft contrast of a sepia lens, in the hallowed halls of the Convento da Santa Monica, the morning light streaming in squares through the iron windows, the nuns are busy bleaching their habits with egg whites, the yolks plopping one after the other in a bowl nearby. Sister Bebiana, quite a trailblazer then and now the queen of Goan dessert, feels her zero-waste instinct kick in. To think of all the egg yolks going to waste! She is quick to invent a use for it-a seven-layered sticky cake using egg yolks, coconut milk, sugar, ghee, flour, and a dash of nutmeg, which has since evolved to include more of the distinct caramelised layers (it's said, the Augustinian priests loved it ...