You cannot simply swap them one-for-one by volume and expect the same result. Think of it like swapping a fluffy cashmere sweater for a heavy denim jacket—they both keep you warm, but the texture is completely different. The cornstarch in powdered sugar is the secret agent that thickens frostings and prevents sauces from getting gritty.
Here is the golden rule: For every 1 cup of powdered sugar your recipe calls for, you will need about 1 cup of granulated sugar plus 1 tablespoon of cornstarch. Yes, you are literally making your own powdered sugar at home. It’s a modern version of an old-fashioned kitchen trick, and it works like a charm.
The Blender Trick (Your New Best Friend)
Grab your high-speed blender, a clean coffee grinder, or even a food processor. Add the granulated sugar and cornstarch—use the ratio above—and blitz it on high for about 30 to 60 seconds. Stop and scrape down the sides if you see any stubborn crystals floating around.
You’re looking for a cloud of fine, silky powder that billows up when you open the lid. Let it settle for a minute to avoid a flour-like explosion in your kitchen. Pro tip: Never grind sugar for too long, or you’ll risk melting it into a sticky mess—trust us, that’s a science experiment, not a frosting.
