Sift together flour and sugar in a large bowl. Cut in shortening until mixture resembles a fine crumb or cornmeal texture. Stir in buttermilk with a fork until a soft dough forms.

Turn dough out onto a floured surface, pulling off any pieces sticking inside the bowl. Gather dough into a ball and knead about 20 times, until smooth and elastic. Wrap in plastic wrap and refrigerate for 8 hours to overnight.

Preheat the oven to 425 degrees F (220 degrees C).

Working on a floured surface, roll or pat dough out to 1-inch thickness. Cut into rounds with a 2-inch biscuit cutter or the floured rim of a glass, by pressing straight down and up. Twisting the cutter will prevent biscuits from rising as high. Place biscuits about 1 inch apart on an ungreased baking sheet and allow to rest a few minutes.

Bake in the preheated oven until lightly brown, 12 to 15 minutes. Cool on a wire rack. Serve warm.