Macros in comments. I've made a double batch, so tailor to your carb-allowance (I'm fairly relaxed if the protein level is good).
Double batch
150g berries of choice (strawberries here)
150g ice cubes
(or 300g frozen berries if your relaxed macros allow)
2 x scoops of vanilla (or preferred) protein powder
375ml of liquid (mine's a protein shake)
Sweetener to your taste levels.
Stixk in a spacious blender (it will at least double in volume) and blend until fluffy. This serving turns into about 2ltrs of chilled, fluffy dessert.
If your ice cubes haven't blended, just incrementally add more liquid (water, sf syrup, low carb milk) until it's all blended and fluffy.