Mad Men’s Bryan Batt shares his best advice for entertaining this summer, be it a quiet supper, sit-down dinner party or all-out bash. As Salvatore Romano on Mad Men, Bryan Batt’s artistic flair inspired Sterling Cooper clients. In real life, Batt is the owner of design store Hazelnut New Orleans, author of Big, Easy Style and a regular party host. And although most people go casual when the weather gets hot, Batt sticks to his signature “swellegant” style. Here, he shares his best advice for entertaining this summer, be it a quiet supper, sit-down dinner party or all-out bash. If you missed Batt on Mad Men (his character was unceremoniously…