I don’t know why it took me so long to have dinner at City Grit, the underground supper club in an old schoolhouse-turned-furniture shop on Prince Street. I finally did it last month, and I can confidently say that the operation is entirely deserving of all the hype it’s been getting. Founder Sarah Simmons, who was recently named one of America’s Greatest New Cooks by Food & Wine Magazine, regularly turns out spectacular Southern-inspired meals, but her main mission is to foster collaboration with notable guest chefs (April Bloomfield and Mark Vetri to name a few) to create a sort of culinary salon. On Tuesday, City Grit is launching its new Next Big Thing Series, which will highlight up-and-coming chefs who are on the verge of hitting major-league status. This week features a four-course, Spanish dinner by Jonah Miller, who has cooked in places like Chanterelle, Maialino and Gramercy Tavern since he was 14 years old. Miller plans to open his first restaurant, Huertas, in Brooklyn within the year. Tickets are $55. -K.H.