Sprinkle the gelatin over ½ cup cold water in a large mixing bowl. Let it bloom for 5 minutes. It’ll thicken up and look a little weird, that’s exactly what we want.
Gently heat your vanilla protein shake in a saucepan over low heat. No need to boil. Just get it hot enough to dissolve the gelatin. Think “steamy coffee,” not “lava.”
Slowly pour the hot protein shake into the bloomed gelatin while whisking. This part’s key. Go slow and steady so everything blends smoothly.
Now crank things up. Use a hand mixer or stand mixer on high speed for 5 to 7 minutes. You’re aiming for a pale, fluffy mixture that’s tripled in volume. It should look like soft whipped cream with an airier bounce.
Pour the mixture into a greased or baking paper-lined dish. Smooth the top with a spatula. (Don’t worry if it’s a little sticky, that’s part of the charm.)
Let it sit at room temperature for 3 to 4 hours. It needs this time to firm up and take shape, so resist the urge to poke it every 10 minutes (we’ve all been there).
Once set, slice into squares, take a moment to admire how fluffy they are… then snack away!