In large bowl, whisk together flour, baking powder, sugar and salt. Using pastry blender, 2 knives or fingertips, cut in butter and shortening until coarse crumbs with a few larger pieces. Make well in centre; pour in milk all at once. Stir with fork just until dough clings together.
Turn out onto lightly floured surface; knead lightly 10 to 12 times. Pat out into scant ¾ inch thickness. Using 2 ½ inch round cutter, cut out biscuit, dipping cutter in flour between cuts, making sure to cut straight down and not twisting the cutter, which would seal the edges and prevent them from rising fully. Repeat with scraps once.
Bake on ungreased or parchment paper-lined baking sheet in 450 degree oven until risen, golden and flaky, about 12 minutes.