In a medium bowl, whisk the cornmeal with 1 cup of cold water until smooth. This creates a slurry and prevents the porridge from becoming lumpy when cooked.

Bring the remaining 3 cups of water and the coconut milk to a gentle boil in a medium saucepan over medium-high heat. Add the salt, ground cinnamon, and grated nutmeg.

Gradually pour the cornmeal slurry into the boiling liquid while whisking continuously. Keep whisking for about 3 to 4 minutes to ensure no lumps form as the mixture thickens.

Reduce the heat to low, cover the saucepan, and let it simmer for 12 to 15 minutes. Stir occasionally, scraping the bottom of the pot to prevent the porridge from sticking or burning.

Once the cornmeal is cooked and the texture is thick and creamy, stir in the vanilla extract and sweetened condensed milk. Simmer for 1 more minute, then remove from heat. Serve immediately in warm bowls, optionally topped with an extra sprinkle of cinnamon or nutmeg.