In a medium saucepan, combine the rolled oats and milk. Bring to a gentle boil over medium heat, stirring occasionally.
Once boiling, reduce the heat to low and simmer for about 5 minutes, or until the oats are tender and the mixture thickens.
In a separate bowl, whisk together the eggs, brown sugar, vanilla extract, cinnamon, and salt until well combined.
Gradually add the egg mixture to the cooked oatmeal, stirring constantly to prevent the eggs from scrambling.
Cook for an additional 2-3 minutes over low heat, stirring continuously, until the oatmeal reaches a creamy custard-like consistency.
If using, stir in the raisins and chopped nuts, and cook for another minute.
Remove from heat and let cool slightly before serving.