Bring water and milk to simmer in large saucepan over medium heat.
Meanwhile,melt butter in a skillet over medium heat.
Add oats, stirring constantly, until golden and fragrant.
About 2-4 minutes.
Once oats are toasted and milk mixture is simmering, stir in oats and reduce heat to medium-low and simmer.
Continue to simmer and stir gently until mixture thickens and resembles gravy.
About 20 minutes.
Add salt
Add vanilla, if using
Continue stirring, gently until oats absorb most of the liquid.
Oatmeal should be thick and creamy. About 7-10 minutes.
Remove from heat and let sit uncovered for 5 minutes.
Spoon into bowls and top with desired topping.