The sourness of the limes sets off its temple-aching sugariness - Nigella Lawson
The verdict: This is a good pie. In a way, it's not so much a pie as a base with some light, fluffy filling that is the most unfilling pie filling I've ever had. Confused? Sorry. I was at first too - really, I was expecting the kind of creamy, citrus-intense filling you get in a lime (or lemon) tart. Even though I read the recipe and saw that you are to whisk egg whites, it didn't quite sink in. The results are good though.
Unusual or substituted ingredients: None. Lime, biscuits, eggs, sugar. Oh, that said, Nigella herself talks in the intro to the recipe about the fact that you probably won't be able to find key limes and that maybe you can get key lime juice but she just uses regular limes. So it's not so much a key lime pie, as a wannabe key lime pie. Never mind.
Special utensils or cookware: You'll need a springform tin and some way to crush the biscuits for the base. I did it all in the food processor then pressed the crumbs into the foil lined tin with the bottom of a container as above. I must say, it was inspired of me to think of lining the tin. She didn't say to do it but I did it because my tin is showing signs of age. It's a very soft, floppy pie, the foil helped it not fall apart completely once it's done.
Repeatability: I'd do this again quite happily but I'd do some things differently. I think I'd cook it longer and I'd aim to do more accurately what she says, which is to make sure the base goes up the side of the tin a bit more. It's a floppy filling - it needs support.
Sauciness: Very saucy, if, like me, you have a husband who is made infinitely happy by the promise and subsequent cooking of a lime flavoured dessert!
Overall pleasure level: Vastly pleasurable. It's easy to throw together (even with the whisking of egg whites, which is not something I'm thrilled about generally speaking). High pleasure for minimum effort really. We gave it a 7.5 out of ten, because really, it has to be made again and probably even again and again to be perfected.