The best shapes for cheese sauce
A bechamel enriched with cheddar or a similar melting cheese. American, and unembarrassed about it. Thick enough that it sets noticeably as it cools, which is what lets a baked version hold a cut edge.
The cheddar bechamel of mac and cheese. Thick enough to need ridges and bores, which is why elbows and cavatappi own the dish.
Canonical: macaroni, cavatappi.

Campanelle works like a scoop with a grip.

Cavatappi grips sauce three ways at once.

A shell is a scoop.

The cupped shell works like a small spoon.

Elbows are open at both ends, so sauce flows through the cavity instead of pooling against a closed seam.

The curl of the body and the pinched closed end work like a scoop.

The fins and ruffled ridges are the whole point.

The wheel works like a small net.
What we would not put it on
Long strands. The sauce is too heavy to ride a strand and slides off it in sheets before the fork reaches the mouth.
Want it the other way around? Start from a shape in the Pairing Finder.
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From the Almanac
Updates from Pasta Almanac, when there is something worth sharing.