We added 5ml Lagavulin and things got a little more interesting.

It seems like this sour is really dependant on lemons, which might be a part of the tricky nature of the amaretto. Either way, my first try with 1:1:1 whiskey, amaretto and lemon juice turned out to be way sour. I've cut the amount of lemon juice in half, which made the drink way better.
It is quite interesting, given that someone else in the comments found the original recipe to be too sweet.

An absolutely smashing sour, definitely one for the list. Made exactly as per the receipe superb

Amaretto is a bit of thug, so I went 40/20 instead.
Delicious with Speyburn.

Found it a bit sweet for a sour - even using half of the sugar syrup. Added another 1/2 measure of Scotch Whisky and it was much more balanced for us (preferring more dry cocktails). Lovely hints of peat smoke from the Whisky and a strong almond falvour. Citrus helps soften the overall cocktail.

This is not only delicious, it's also really good with a strongly peaty single malt Scotch (I used Ardbeg). I love the smokiness but it's a little bit hard to find cocktails that can really stand up to it. This one can.

I really like this. But I also swap 10ml of the disaronno with 10ml Licor 43 and the result is kickass.