Pizza has been the Donofrios’ stock in trade. The family owns Alfredo’s in Ridge, Old Town Pizza in Port Jefferson Station, Middle Island Pizza and Boccone in Selden. But Philip Donofrio decided to go in another direction last year when he christened a kitchen-trailer “Go Burger” and parked it on the side of Middle Country Road in Ridge.

Now he’s opened a second Go Burger in Mount Sinai, but this one has walls, windows, tables and chairs.

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Both locations focus on burgers, made, Donofrio said, with beef from Pat LaFrieda, the New Jersey meat purveyor that supplies Shake Shack and other high-profile burgeries. Singles are $5, doubles are $7, and toppings include cheese, bacon, avocado, chili, eggs, sautéed mushrooms and peppers.

Go Burger also makes hand-cut fries ($2 for small), Philly-style cheesesteaks ($9), a handful of sandwiches ($5) and milkshakes ($5) in vanilla, strawberry, chocolate and a special weekly flavor such as Butterfinger, red velvet or rainbow cookie. Exclusive to the Mount Sinai location are salads ($6 to $9) and three desserts ($4 to $5): a bag of doughnuts with warm dipping sauce, New York cheesecake and house-made ice cream sandwiches.

Go Burger’s restaurant is at 271 Route 25A, Mount Sinai, 631-432-3331; the trailer is at 1878 Middle Country Rd., Ridge, 631-252-0008,