Add oats, milk, maple syrup, vanilla, cinnamon, salt, and peanut butter into a medium/large pot.
Bring to a boil, reduce the heat to low, simmer uncovered for about 10 minutes, stirring from time to time, until soft. At first, the oatmeal will be very runny but after adding the remaining ingredients and during cooling it will thicken significantly.
Remove the pot from the heat, add coconut oil, lemon juice, and mashed bananas. After a minute or so, your oatmeal should have a perfect creamy, thick, but still pourable consistency.
Pour your oatmeal into bowls and top with your favorite toppings (I like a drizzle of peanut butter mixed with maple syrup, 1-2 chopped cubes of bittersweet chocolate, and roasted and salted peanuts for crunch).
Enjoy!