The simplest isn't a meal, but I love previously roasted chestnuts with sliced bread and butter pickles, the ones I call ”sugar pickles” because they're so sweet.

They don't grow here and I gave up roasting the fresh ones, because too many had worms. :( Chestnut risotto sounds awesome! Cream brings out the chestnut flavor nicely, so adapt any cream sauce. I like them with fenugreek, but fenugreek is one of my vary favorite flavors, so it might just be me. I haven't tried this, but I'm thinking they'd be good with a (American) praline coating, which is a caramel style crunchy candy coating, best when topped with salt (check praline pecan recipes, not pecan pralines which are candy clusters). I'm not a big sugar hound, but it brings out the chestnut flavor, where a lot of savory ingredients mask it.

I pick wild hazelnuts (Alberta) and if I don’t eat them raw, I make hazelnut spread for toast. Delicious and very simple to make. I think chestnuts would work as well.

Or there must be a recipe for chestnut spread.

Chestnuts don’t actually taste very ’nutty’. They are more floury and soft a little more like potato in texture than a nut. They need to be baked or boiled before use and you can’t shell them until they’re cooked. Not sure if the spread would work with them but thanks for the recipe. The praline might work, though.

But we don't eat snacks, cookies or candy, and rarely cake, so I’m really thinking about actual meals using chestnuts.

The risotto recipe contains no cream, but it does have butter and parmesan. https://www.greatbritishchefs.com/recipes/chestnut-risotto-recipe 

So, I was peacefully eating breakfast, and the open bag of roasted chestnuts started talking. The more I ignored it, the louder it got, until it was yelling, ”Butter!” It was a spicy breakfast with no butter. So I grabbed the bag, a tablespoon of butter left from maaking apple pies, and the fenugreek. But the chestnuts wanted to try the praline coating. I didn't want to get a recipe and couldn't even remember if it was coat a spoon, softball or hardball. We compromised. Fenugreek toffee. I argued that fenugreek wouldn't go with dark brown sugar, but they inssisted. I gave in. Just butter, brown sugar, fenugreek and a little flor de sal. I took my revenge by squishing the chestnuts to break them up rather than cutting. As you can tell from the arguments, this wasn't a great idea. I was right about the brown sugar not playing well, and it made the fenugreek a bit bitter. I mean, it was good, and it got ’et all up, but I think listening to dead things that never had any processes of cognition and communication to begin with is not a fruitfull endeavor. :) Given the results, however, I think the praline treatment would be success.

I like to combine roasted chestnuts with halved Brussels sprouts, sauteed in browned butter, seasoned with salt & pepper and a little nutmeg.

Make your own marrons glacés for christmas. Delicious.

https://www.marmiton.org/recettes/recette_marrons-glaces-faciles_24480.aspx

Have you tried in a white wine sauce with chicken or fish? I'm thinking it would taste really good, and be an interesting twist from standard Autumn fare.

Thinking on the idea of nut butter, especially for the crumbs, how about making a paste with olive oil and spices, maybe even some seeds, and spread on toasts or filling roulades. Or for sweetish, but not candy, with just a small amount of fig. Or go American seasonal with cranberries. :)

My neighbour's daughter lives in the Corrèze where they have a lot of chestnut trees and they make a paste that you can spread on bread, use in desserts.....https://www.cuisineactuelle.fr/recettes/pate-de-marrons-275649

or a purée that would be delicious with roast pork or chicken https://www.cuisineactuelle.fr/recettes/puree-de-chataignes-264470

The final experiment. Chestnut chocolate truffle cake, an extremely easy no cook fridge cake.

The chestnuts have all gone now. I’d make the risotto and cake again but I wouldn’t bother with the pie. Thanks for all the ideas. If anyone has any more brainwaves for main course, no meat, savoury dishes I’d be interested. It does seem that a lot of chestnut recipes call for a good deal of sugar.

Apologies for the chicken suggestion. I'd forgotten the mostly vegetarian requirement.