Today is National New England Clam Chowder Day, and shouldn’t be confused with February 25’s National Clam Chowder Day. Today’s holiday celebrates the rich milk or cream based chowder that’s preferred in Massachusetts and points north. And Oyster House owner Sam Mink is observing it by slinging New England-style chowder street-side near 15th and Sansom streets for $5. Next month’s clammy holiday honors the tomatoey variety of chowder preferred by New Yorkers. There’s no word yet if Mink will be back out on the street for that yet.