Blend the frozen berries in a high-speed blender until smooth, about 30–45 seconds.

Add freshly squeezed lemon juice and icing sugar, then blend again for 20–30 seconds.

Whip the egg white in a separate bowl until soft peaks form, then gradually add to the berry mixture while blending on low speed for 15–20 seconds.

Transfer the mixture to a freezer-safe container, cover tightly, and freeze for at least one hour.

Let the sorbet soften at room temperature for 5–10 minutes before serving.

Garnish with fresh berries or serve with shortbread cookies if desired.