Place the chopped rhubarb, 100 g caster sugar, lemon juice and pinch of salt in a saucepan. Cook over medium heat for 8–12 minutes, stirring occasionally, until the rhubarb is very soft and the liquid has reduced.

Mash the cooked rhubarb or briefly blend it into a fairly smooth purée. For a stronger ripple, reserve 3–4 tablespoons of the cooked pieces before blending, then cool the compote completely for 30–45 minutes.

Whip the cold cream in a large bowl until soft or medium peaks form. Stop as soon as the cream holds its shape, because overwhipping can make the final ice cream heavy and grainy.

In a separate bowl, stir together the sweetened condensed milk and vanilla extract. Add the remaining 50 g sugar only if you prefer a sweeter result, since the condensed milk already provides considerable sweetness.

Fold the condensed-milk mixture gently into the whipped cream. Use a large spatula and slow strokes so the mixture stays light and airy.

Spoon half of the ice-cream base into a freezer-safe container. Add some rhubarb purée, top with the remaining ice cream and spoon the rest of the rhubarb over the surface.

Swirl the layers lightly with a skewer or knife, making only a few loose passes. Cover the container tightly and freeze for at least 6 hours, preferably overnight.

Set the frozen ice cream at room temperature for 5–10 minutes before scooping. Serve in chilled bowls or crisp cones, with extra rhubarb ribbon visible on top if desired.