Start by measuring out completely frozen mixed berries and placing them in a high-speed blender. Blend on medium speed for about 30 seconds until roughly crushed.

Pour in icing sugar and a squeeze of lemon juice. Blend for an additional 30 seconds until well-combined and slightly smoother.

Whip the egg white in a separate bowl until soft peaks form. With the blender running on low, gradually add the whipped egg white to the berry mixture.

Transfer the blended mixture into an airtight container, smoothing out the top. Seal and freeze for at least 1 hour.

Once set, let sit at room temperature for 5-10 minutes before serving. Use a chilled scoop to serve into bowls or glasses.