Irish whiskey is often matured in oloroso sherry seasoned casks so it's no surprise that whiskey and sherry blend harmoniously in this cocktail, with lemon...
No groseille syrup so used creme de cassis. No Lustau Don Nuno; used our open bottle of Osborne Oloroso "Special Sherry" from the depths of Osborne's cellars, which is richer than Don Nuno so I cut it back to 1 oz but it still totally overwhelmed the drink. MacElhone and Craddock just call for "sherry": fino? amontillado? PX? It matters. An equal amount of oloroso is overkill but might be ok for fino. Also think the lemon juice should be cut back even more to 1/4--1/3 oz.
I can confirm for any curious/desperate cocktail enthusiasts in the UK that this works with 1 tbsp redcurrant jelly if you stir it in with the lemon juice to dissolve. Probably a touch drier due to the lower sugar content than a syrup would have, but a perfectly tasty drink!
A tasty classic. I used Gifford's Grenadine. Might have been my sherry but it was a little sweet - so I marginally upped the whiskey and reduced the sherry and syrup. A punchier drink, which went down well. And more of an "Artisht's Shpeshul" after a couple...