Firestone Walker's Velvet Merlin oatmeal stout has been transformed into a mindblowing mouthful known as Nitro Merlin Milk Stout. The new ingredient is lactose, a.k.a. milk sugar. When Velvet Merlin is brewed with milk sugar to create Nitro Merlin Milk Stout, the effect is similar to adding cream to your dark roasted coffee. The wizardry comes via “nitro,” the brewing nickname for nitrogen gas.