I had honestly never head of Milk Bar before but my sister wanted to go here when we were in Vegas a few weeks ago. She said that it was popular in NY. We had dinner at Momofuku next door which is also the same company as Milk Bar.
Milk Bar is located inside the Cosmopolitan Hotel in Las Vegas.
They are known for their Cereal Milk Soft Serve and Crack Pie. I got to try their cereal soft serve and it was just okay. It's pretty much just vanilla soft serve with corn flakes. I wouldn't go out of my way to get it. My sister ordered the crack pie and compost cookie. I didn't get feedback from her on her opinion. Since we were full she saved her treats for later.
We had just come from dinner so I wasn't that hungry but they do look like they have a pretty unique dessert menu. Maybe grab a treat if you're already in the hotel but I would make a trek out here just to get dessert.