Add the cottage cheese to the blender and secure the lid firmly. Blend on medium to high speed until the mixture is completely smooth and creamy, stopping once or twice to scrape down the sides if needed. This step is essential for removing any grainy texture and creating a mousse-like base, so take your time and blend until it looks silky and uniform.

Add the lime juice, lime zest, sweetener, vanilla extract, and a small pinch of salt to the blended cottage cheese. Blend again until everything is fully incorporated and the mixture looks evenly mixed. Taste at this stage to check the balance of tanginess and sweetness, since lime intensity can vary, and make small adjustments if needed.

Add the protein powder and Greek yogurt if you’re using it. Blend on medium speed until the mousse becomes thick, smooth, and creamy, making sure no pockets of dry protein powder remain. Scrape down the sides of the blender once more to ensure a consistent texture throughout.

Taste the mousse and adjust as needed. If it’s too tart, add a little more sweetener and blend briefly. If the texture feels too thick, add a tablespoon of milk or water and blend again. If it feels slightly loose, that’s fine—it will thicken as it chills.

Transfer the finished mousse into individual serving containers or jars using a spatula to get every bit out. Cover and refrigerate for at least 30 minutes before serving to allow the mousse to set and develop its creamy, pie-like texture.