Most coffee shops sell biscotti to have with your coffee. I've always wondered, is there a 'correct' way of consuming them together? Are biscotti ideally consumed with a certain preparation of coffee (e.g. a capuccino but not a latte)? Should I be dunking, or is that frightfully uncultured?
Adapting "Golf is a good walk spoiled," (whoever said it; Twain probably didn't), biscotti is a sure way to destroy a good coffee.
The soft, cookie-like biscotti available in many cafes won't hold up to any dunking at all, and will end up waterlogged and sad at the end of your sipping. The break-your-teeth traditional biscotti seem to call for something, but they don't seem edible to me. I prefer the middle-of-the-road, softer, chewy biscotti that can be enjoyed without submerging in liquid.
At the risk of this becoming an opinion-based discussion, for my money: If you want to drink coffee, just drink coffee. If you want to eat a soggy cookie, eat a soggy cookie... but don't combine the two and risk ruining your perfectly good coffee in the process. :)
There actually is a scientific equation for determining how long and at what angle to dunk something in coffee. Len Fisher won the Ig Nobel in Physics for working out the equation in his paper "How to Dunk a Biscuit". He is British, so in my American copy of his book the paper is titled "How to Dunk a Doughnut" but the equations he works out would also suit biscotti.
A lot of it comes down to the makeup of the biscotti you are eating. As @hoc_age mentioned some store "biscotti" are just kinda hard cookies and some are teeth-breaking dense blocks. Using Len Fisher's equations though you could determine how long you could dunk the biscotti to soften it up without it collapsing into and ruining your coffee.
In the end I agree with @hoc_age, defend your coffee from invasion but to each his own, at least science has an answer!
I know quotes are better than links but I can't find a public source of the paper and it would be too long to post here. I did find a BBC article from 1999 when he won the award: http://news.bbc.co.uk/2/hi/science/nature/462987.stm
Speaking from family experience (my family is french). My father's breakfast consisted of hard stale bread which he would dunk into a cafe au lait. (Same as my uncles.)
They never did that with espresso - only with the morning cafe au lait. When I'm in France I see the older generation still doing that in the morning - it's less common amoung the younger generation.
As a side note "to dip one's biscuit" has a sexual connotation in French.
Here is a link to "how to dunk a biscuit" paper @justin-c mentioned, which is surprisingly on Nature. https://www.nature.com/articles/17203
Here I quote his main contribution for solving the great conundrum from science perspective.
All I had done, in fact, was to write down the Washburn equation, derived2 in 1921 to describe capillary flow in porous materials:
where t is the time for a liquid of viscosity η and surface tension γ to penetrate a distance Linto a fully wettable, porous material whose average pore diameter is D. The equation is strictly true only for capillary flow in a single cylindrical tube in the absence of gravitational effects, but can be extremely accurate for more complex materials, including, as I found experimentally, biscuits. Why this should be so is a very interesting question. In practice, I could use the Washburn equation to predict how long different biscuits could be safely dunked by the physicist'smethod, the longest dunkers generally giving the best flavour release (to my palate at least).