Prepare the Raspberry Puree:

1. Puree the Raspberries: In a blender or food processor, puree the raspberries until smooth. If you prefer a smoother texture, strain the puree through a fine mesh sieve to remove the seeds. Set aside.

Whip the Cream:

2. Whip the Heavy Cream: In a mixing bowl, whip the heavy cream with a hand mixer or stand mixer until it forms soft peaks. Be careful not to overwhip. Set aside.

Prepare the Egg Whites:

3. Whip the Egg Whites: In a clean, dry bowl, whisk the egg whites with a hand mixer or stand mixer until they begin to foam. Add the cream of tartar, then gradually add the powdered sugar and continue whipping until stiff peaks form.

Combine the Mixtures:

4. Mix the Raspberry Puree and Sugar: Gently fold the granulated sugar and vanilla extract into the raspberry puree.
5. Fold in the Whipped Cream: Carefully fold the whipped cream into the raspberry mixture, ensuring it’s fully incorporated without deflating the cream.
6. Fold in the Egg Whites: Gently fold the whipped egg whites into the mixture, working in batches if necessary to keep the soufflé light and airy.

Freeze the Soufflé:

7. Transfer to a Mould or Serving Dish: Pour the mixture into a soufflé dish, loaf pan, or individual serving cups.
8. Freeze: Cover the dish with plastic wrap and freeze for at least 4 hours, or until it’s firm and scoopable.