Sours are a diverting way of consuming serious liquor. The whisky sour, according to legend/Wikipedia, should strictly be a whiskey sour - the 'e' denoting bourbon whiskey rather than Scotch whisky. But Scotland might debate this, having muscled in on the act too, and more significantly here, I didn't have any bourbon to hand.
60ml (2oz) scotch whisky
1 egg white
Half a teaspoon of sugar (or a dash of sugar syrup)
10ml lemon or lime juice
Shake the ingredients, like billio, in a cocktail shaker with ice. Strain into a glass tumbler full of ice.
The egg white, if shaken with sufficient animation, will leave the drink delightfully smooth and light, while the citrus and sugar should combine to achieve a sweet/sour balance of Buddhist integrity.
Happily, my selection of the distinctly un-peaty Glenmorangie 10-year-old was consistent with Bar-Blog's advice, in an interesting post on the history of whisk(e)y sours, to avoid the stronger, smokier styles of Scotch that might throw the drink off kilter.
Even so, I have a hunch the sour works better the traditional way, with bourbon, which means my work here is not yet done.