Buttermilk adds a subtle, creamy tang to the grits.
Bring water, whole milk, and salt to a boil in a medium saucepan over medium-high. Gradually whisk in uncooked grits; return to a boil. Reduce heat to medium-low, and simmer, stirring occasionally, until creamy and thickened, 25 to 30 minutes. Remove from heat, and stir in buttermilk and butter.
Stir pumpkin, maple syrup, pepper, and pumpkin pie spice into warm grits. Sprinkle servings with spiced pecans.