The Mellow sous-vide is getting a second-generation version, with Mellow Duo adding a dual-vat option to the all-in-one cooking system. Launched back in 2014, in the early days of domestic sous-vide, the first-gen Mellow promised smarter meals with added convenience features like refrigeration. Now, it’s getting an update. I was a backer of the first-gen Mellow project, though it didn’t …