Matyson - the much-honored BYOB on 19th Street off Rittenhouse Square - has closed, its former chef, Ben Puchowitz, confirmed.

Puchowitz said the restaurant's owner - his father, Butch - was "ready to retire. He's sad and relieved at the same time."

Matyson's last night of service was Friday, July 3 and its Facebook page offered no indication that this was the finale. OpenTable is still offering reservations. Staffers said they were told of the closing Monday morning.

The new occupant, attempting to open by the end of August, is Milkhouse, which specializes in grilled cheese and milkshakes. Its first location opened last fall inside Suburban Station.

Restaurateurs Matt and Sonjia Spector, with Matt's cousin Butch Puchowitz, opened Matyson in November 2003 in Puchowitz's former butcher shop. (The Puchowitz family owns the bricks, according to city records.)

When the Spectors moved to Napa four years later, Ben Puchowitz - backed by Brian Lofink (now of Sidecar Bar, Kraftwork, and Kermit's) - took over the kitchen.

Ben Puchowitz left the business a couple of years ago. With business partner Shawn Darragh, he opened Cheu Noodle Bar in Washington Square West and Bing Bing Dim Sum on East Passyunk Avenue.

Sonjia Spector, who with her husband own JoLe in Calistoga, Calif., posted a farewell message on her Facebook, reading in part: "It has been a long time since we worked with you wonderful, weird, crazy, dedicated, quirky people, but today we have you all in our hearts. 12 years is an amazing run."

Post updated to identify new occupant