Maple Raisin Steel Cut Oatmeal

• 1 cup steel cut oats
• 1 and 1/2 cups milk
• 1 and 1/2 cups water
• 1/4 teaspoon salt
• 1/4 cup maple syrup (preferably pure maple syrup). 1/3 cup raisins
• butter - if desired
• chopped walnuts (or other chopped nut) - if desired