We all know what lasagne is. A baked pasta dish, consisting of alternating layers of pasta sheets, a ragù/bolognese sauce and a bechamel/white sauce.

Obviously, there’s room for a lot of variation in the constituent sauces, especially in the recipe for the ragù. But once the sauces are made, putting them together into the lasagne is straightforward, right?

Wrong. It turns out it’s not quite so simple.

I was making a lasagne recently, and when it came to the assembly stage, I hesitated. I knew what order I thought the layers should go in, but this time I decided I’d check to see how others did it.

First I consulted my go-to reference work: Leith’s Cookery Bible. And Leith’s recommended layering was quite different to mine. So then I asked around a few friends, and consulted a few more books, and was surprised to find an extraordinary range of variation, purely in the order of layers.

Before I go any further in describing my findings, let’s establish some notation.

Let’s describe the structure of a lasagne by writing a sequence of letters representing the layers. The letters will be in the order that those layers are placed in the dish, from the bottom up. The letters are as follows:

R = red sauce, i.e. bolognese, ragù, whatever you want to call it. It could be meat-based or vegetarian. Obviously there are infinite variations in how you make it, but for the purposes of this analysis, it’s all the same.

W = white sauce, i.e. bechamel. Again, there are many variations: addition of bay leaves, parmesan, pesto, etc.; or even a cheat’s bechamel, e.g. crème fraiche. Again it’s all the same for the structural analysis.

P = pasta, i.e. lasagne sheets. The only real variation here is that some people apparently cook the pasta first, which seems to miss the point that it’s meant to absorb liquid from the other layers to thicken the lasagne, but again I’m going to treat it all the same.

C = cheese. Usually grated cheddar or parmesan, possibly mozzarella. A pure cheese layer almost always appears as the top layer, but some use it elsewhere too.

We just need one more bit of notation. Quite a few people give the instruction to “repeat until you fill the dish”, or similar. To cover this, let’s use brackets () to indicate that the sequence of layers inside the brackets is to be repeated a number of times:

(x) = repeat x a number of times

So, for example, (PRW) means pasta, red sauce, white sauce, repeated.

Now we have a notation, we can start to explore the possible variations in structure.

First, my version, as well as that of my family (which may explain where I got it from), several friends, and also Larousse:

(RPW)C

Then there’s the Leith’s Cookery Bible version:

(PRW)C

Here are a few more variations I discovered in the wild:

(PRW)PWC
(WPR)WPWC
(RWP)C
(RWP)RWC – the Mary Berry version
(RPWP)RPWC
(RPWP)WC
(RP)WC
(WRP)WC
(RPWC)

Can we make any sense of this? I think so.

There are two areas for variation: the cycle and the finish. In theory, one could have a variation in the start as well, but I didn’t find any examples of this.

The cycle

The cycle is the sequence of layers which is to be repeated: the bit inside the brackets in our notation. At first, it looks like there are a lot of possible different cycles. But actually the number can be reduced. For a 3-layer cycle, with one each of R, W and P, there are two basic versions:

The alpha cycle: (PRW)
The beta cycle: (PWR)

These two cycles are the reverse of each other: if you do the A-cycle in reverse order, you’re doing the B-cycle.

Which is correct? I’m not going to attempt to answer that. The beta cycle was more common among the people I surveyed. But the alpha cycle follows the intuitive idea that white sauce should be layered onto red sauce, rather than the other way around.

I’ve defined both cycles starting with pasta. But they can and do start from any layer. They can start with the white sauce:

(WPR) = alpha cycle, second inversion
(WRP) = beta cycle, first inversion

Or they can start with red sauce:

(RWP) = alpha cycle, first inversion
(RPW) = beta cycle, second inversion

Sauce on the bottom means you don’t need to butter the dish, but the advantage of pasta on the bottom is that it provides more structural integrity: you should be able to take a slice cleanly out of the dish without anything falling out of the bottom.

Beyond these six variations on the three standard layers, there are a few wackier possibilities. For these, you either have to add something or take something away.

The only conceivable option for taking something away is the white sauce. Without the red sauce, you’d just have a weird version of macaroni cheese with lasagne sheets; without the pasta you’ve got a creamy, layered casserole. Hence the only 2-layer cycle found in my survey is the (RP) cycle.

What about adding something? Well, there seem to be two popular options.

First, the “cheesy overload” option where a layer of grated cheese is added on top of every white sauce layer: (RPWC) and derivatives.

Then, you’ve got what I call the “toddler variation”, where you feel squeamish about the red and white sauces touching each other, and insist on separating them all with pasta sheets: (RPWP) and derivatives.

The finish

It seems to be universal to finish with a layer of cheese: -C

And almost universal to finish with white sauce then cheese: -WC

In fact only one respondent didn’t finish with -WC, finishing instead with -PC. I call this finish “the carapace”. I can only imagine the creator of this enjoys smashing through the hard lid of dry, crunchy pasta and baked cheese to get to the soft innards of their lasagne.

It’s fairly common to finish with pasta, then white sauce, then cheese: -PWC

Aside from the carapace, there are only two variations above which don’t finish this way: Prue Leith’s and Mary Berry’s. Everyone else seems to feel that there should be no red sauce above the last pasta layer. Prue and Mary are happy with exposed meat.

As far as I can tell, aside from the carapace and Mary Berry’s exposed meat, all the apparently different finishes in the variations above are just what you need to do to finish with -PWC from your chosen cycle.

One elegant property of the beta cycle second inversion, (RPW), is that all it needs is a -C finish on top of the last repetition to achieve the classic -PWC finish.

However, I’m not sure that’s a good enough reason to choose the beta cycle over the more intuitive alpha, and I find the argument for pasta on the bottom compelling. So, for my next lasagne, I think I’ll try:

(PRW)PWC

Pasta on the bottom for structural integrity, white-on-red layering, and the classic -PWC finish.

Addendum

Long after doing the survey, I discovered the wonderful Alvin Zhou. His 100 hour lasagna recipe uses the following layering:

R(PRW)PWC

Interestingly, this is the first version I’ve seen where there’s a separate start before the cycle. Zhou opts for the alpha cycle (although his white layers are barely there at all), but precedes this with a red layer on the bottom of the dish, before the first pasta layer.

Actually, what he’s doing is a single beta cycle RPW with a repeated alpha cycle (PRW) inserted into it, finished with cheese.