In a large saucepan over medium-high heat, combine the evaporated milk, water and kosher salt and bring to a boil, whisking occasionally to break up any skin that forms on the surface.
Lower the heat to medium and add the polenta in a steady stream while whisking to combine. Once the liquid has been absorbed, lower the heat to low and cook the polenta for 5 minutes, whisking continuously.
Whisk in the Parmigiano-Reggiano, followed by the goat cheese and Brie. Add pepper to taste and serve immediately.