It being Thanksgiving I baked a lemon meringue pie. I’ve been doing that for many years…and for most of those years the results, while tasty, were pies whose lemon filling didn’t set up well.

That changed a couple of years back when I found a recipe that explained the chemistry of what’s going on with the filling, and how you have to balance a variety of factors to be successful:

• Corn starch thickens stuff by absorbing water into small globules…but overheating the globules causes them to burst, undoing the thickening.
• I love tarter pies. But trying to make a lemon meringue pie tarter by using more lemon zest or lemon juice raises the acidity…which keeps the starch globules from forming properly.
• You can’t heat the egg yolks too much or their proteins will denature, and you’ll end up with something like scrambled egg bits in the mist of your custard.

Sadly, I lost the link to that recipe. But I found another one this year which comes together in a different way that’s logistically a lot simpler. You can find it at Harriett’s Cooking. She also offers a different recipe for the meringue which simplifies the final baking process.

What’s different about her pie recipe? Primarily two things. First, it uses six egg yolks, not four¹. Second, you don’t have to do a back-and-forth involving the egg yolks and the sugar/starch/water mixture.

Instead, you whisk together all the non-water ingredients with a half cup of water and slowly whisk in one cup of boiling water to the mixture. After which you bring everything to a low bubble, and then simmer for no more than 60 seconds, add in the butter, and pour the result into a pre-baked pie shell. It sets up beautifully!

The final result is delicious. Definitely worth checking out!

1. Which complicates making the meringue a bit, because her meringue recipe only calls for four egg whites. NB: throw out the whites from two of the eggs when you extract the yolks. ↩