Yum! This was a home run. It's a little hot here for mac'n'cheese, but I had a beautiful heirloom cauliflower (who knew there were heirloom cauliflowers?) and garden tomatoes that needed using, so it was meant to be. Modifications: Used all gruyere cheese, substituted whole-milk Greek yogurt for creme fraiche, thinned out heavy cream with 1/4 cup 2% milk, used panko instead of fresh breadcrumbs, and forgot the mustard. Oh, and I also augmented the vegetables with 4-5 large shallots. Everyone loved it, even the kids, who are not normally big cauliflower fans. Leftovers were devoured for next day's lunch. Time and heat-saving tip: Because my kitchen was sweltering, instead of saving the pasta for last last, I cooked it right after the tomatoes and left it in the colander (placed inside the empty pot) while I sauteed the vegies and made the bechamel. Any stuck-together pieces loosened right up as soon as I mixed in the vegetables and sauce, and I didn't have to have that pot of hot water in my kitchen for an extra half hour.