I'm almost embarrassed at how easy this is but, as you will find out, simple though it is to make, its flavor is deep, complex and utterly compelling.
So, here's how it goes: you don't make a custard and you don't need an ice-cream maker. You could (and I often do) serve it with a chocolate sauce but my absolute favorite way of eating this is by squidging it into little brioches, like sweet burger buns, as they do in the south of Italy. Luckily, I live near an Italian caffe that will sell them to me, but I am also searching dutifully for an online source.
I use Illy espresso liqueur here, but any coffee liqueur would do, even if it weren't quite as strong. I have never tried using regular instant coffee granules in place of the instant espresso powder stipulated, though I dare say if you boosted quantities and dissolved the granules in a little boiling water first, you could make it work for you. But this works so perfectly for me that I have no desire to meddle. And I whip up this ice cream so often, it makes comforting sense for me to keep the key ingredients in stock.
Maybe I don't have to add this but as a security measure, let me remind you that 1 tablespoon is 3 teaspoons. My instant espresso powder comes with a teaspoon measure inside, so, if it helps, use 6 of these to make sure you are adding the right amount.
Put the condensed milk in a bowl and stir in the espresso powder and liqueur. In a separate bowl whisk the cream until it reaches soft peaks. Fold the cream into the condensed milk mixture, then pour this gorgeous caffe latte-colored airy mixture into an airtight container and freeze for 6 hours or overnight. Serve straight from the freezer.
Reprinted from Nigellissima. Copyright (c) 2012 by Nigella Lawson. Published by Clarkson Potter, a division of Random House LLC. All rights reserved.