In a saucepan, heat 100 grams of sugar on low flame until it melts and turns golden brown. Stir occasionally to avoid burning.
Carefully add 50 ml of warm water to the melted sugar and mix well. Cook for another 2-3 minutes until the butterscotch sauce thickens. Remove from heat and let it cool.
In a separate bowl, whisk 500 ml of heavy cream until soft peaks form.
Add 200 grams of sweetened condensed milk to the whipped cream and mix gently.
Pour the cooled butterscotch sauce into the cream mixture and fold gently to create a marbled effect.
Transfer the mixture to an airtight container and freeze for at least 6-8 hours or overnight for best results.
Scoop out the butterscotch ice cream and serve chilled.