Go to the Recipe: Sous Vide Chawanmushi
In theory it should work. The only issue will be heat being transferred from all sides but the top. It may take longer.
Is it necessary to use a fully submerged, sealed, screw-top jar? Could I use a traditional chawanmushi vessel in a sous vide bath that only comes up almost to the lip of the vessel and just use a lid that sits on top?
Would just like to point out that 120g of diced mushrooms is quite a lot. It's good to just eat on its own, but you will have a ton of extra. Even half that amount yields plenty of mushroom to top the dish
It will.
You absolutely can. But Nick recommends reducing the amount by 25% to start.
Can I substitute with regular soy sauce?
Would putting the custard base under vacuum briefly help to eliminate bubbles?