Preheat the oven to 450°F. Lightly spray a large baking sheet (13" x 8") with cooking spray, line with parchment paper and spray again. Set aside.
In a large measuring cup or a medium size mixing bowl, combine milk, buttermilk. Whisk well and set aside.
In a food processor, combine flour, baking powder, baking soda, salt and sugar - pulse until combined.
Add the cubed, chilled butter and pulse until a coarse, sand like mixture forms.
Remove the flour mixture into a large mixing bowl; add the wet ingredients and mix until just combined. Set aside for 5 minutes.
After 5 minutes, stir the batter once and pour onto the prepared baking sheet and smooth the top with a spatula. Sprinkle with your choice of toppings.
Bake in the preheated oven for 12~15 minutes or until a cake tester inserted into the center comes out clean.
(Optional Step) To get a golden brown top, turn on the oven to broil for 1~2 minutes.
Let cool slightly before cutting into squares and serving. Serve warm with maple syrup.