In a medium saucepan, mix 2 cups of water, milk, farina, salt, vanilla, cinnamon, nutmeg, and sugar to taste. Stir until combined.
Let the mixture rest for 5 minutes.
Heat the saucepan over medium heat stirring constantly to prevent it from sticking to the pot. When it breaks into a boil, add butter and lower the heat to very low. Simmer and stir until it reaches the desired consistency, taking into consideration that it will get much thicker when it cools down. Aim for a thick but still liquid consistency.
Remove from the heat and pour into individual servings and sprinkle with cinnamon or nutmeg on top. Serve warm.
Notes
If the mixture becomes too thick, you can add in a bit of extra milk at the end. Generally, this will have a pudding-like consistency.