Yeah, I can get on board with the Kit Kat cross-finger munchers, they want the world to burn. But there is a specific ancient Japanese practice of palate placement that accurately specifies the order in which particular taste sensations should occur for maximum enjoyment of each mouthful of food.
It is actually why you *should* eat a nigiri (ie, a slab-style sushi piece, such as I have pictured) by placing it rice-side UP on the tongue, so the fish, meat or tamago (omelette) piece tickles your tastebuds first. The iron, salt and delicate sweetness of the fish flavouring develops on the palate, and then the more bitter, sour vinegared rice afterwards. Basically the salt should be prominent first, then the sweet, and then sour, and then salt again.
So when eating a chocolate digestive, you should actually eat it with chocolate facing UP, in order to let the salty, malt oat biscuit melt on the tongue before developing into the sweet, creamy chocolate for a full flavour development. This is why custard creams and other sandwich biscuits are so addictively brilliant; if our tongues experienced the cream on the outside (think, an inverted custard cream) before the biscuit, then the biscuit would be overwhelmed and the salty, grain, butter tastes would be lost.