Boil 1 cup of water until it reaches a rolling boil. Add the raspberry gelatin powder and collagen powder to the hot water, stirring constantly for about 1-2 minutes until both are completely dissolved with no visible powder remaining. The heat is essential here—it ensures the gelatin fully hydrates and the collagen dissolves smoothly, which prevents lumps in your final dessert.

Allow the gelatin mixture to cool to room temperature—this takes about 15-20 minutes and is crucial because adding cold yogurt to a hot mixture can cause the texture to become grainy. Once cooled, add the Greek yogurt and vanilla protein powder, whisking vigorously until the mixture is completely smooth with no streaks of yogurt visible. I like to use a whisk rather than a spoon here because it incorporates the ingredients more evenly and creates that signature fluffy texture by adding tiny air bubbles.

Let the mixture rest at room temperature for 5 minutes to allow the gelatin to begin setting and the flavors to meld slightly. Divide the fluff evenly among 4 serving cups, then refrigerate for at least 2 hours until the dessert is fully set and has a jiggly, mousse-like texture. You can make this up to 24 hours ahead—it actually holds up beautifully in the fridge.

Remove the fluff cups from the refrigerator and top with fresh raspberries just before serving for the best color and texture contrast.