Shake Shack is teaming up with North End mainstay Mike’s Pastry to debut the very Boston-sounding Lobstah Shell concrete for their Harvard Square location. The vanilla custard-based concrete features crispy Lobster Tail pastry shell from Mike’s with strawberry puree and ricotta cream. The collaboration comes on the heels of Shake Shack’s other Boston area institutions — including the Coppa Burger with Chefs Ken Oringer and Jamie Bissonnette in honor of their 100th location in the Seaport and the Whoopsie Pie Oh My concrete, which blends South End Buttery’s chocolate whoopie pie into a vanilla custard. 

And likewise with previous local collabs, Shake Shack teamed up with local drop-in org Youth on Fire — a non-profit that provides confidential educational programs and support for homeless and at-risk youth — to donate five-percent of all sales from the Lobstah Shell Concrete ( $4.59/small; $6.79/large)  through Dec. 31. So forget the freezing cold — it’s time to indulge. And indulge often.