If you’re using a sugar thermometer, aim for 118-120°C (235°F). Without one, use the cold water test above: drop a little of the boiling mixture into a bowl of cold water. At soft-ball stage it forms a soft ball you can flatten between your fingers – if it just spreads into the water it needs longer, if it holds a firm shape it’s gone too far.

This recipe is measured against a standard 395g tin of sweetened condensed milk, the size sold in most NZ supermarkets. If your can is a different size, weigh out 395g rather than using the whole tin – too much condensed milk changes the sugar-to-liquid ratio and is one of the more common reasons fudge won’t set firm.

Readers are split. Several have halved the 4 cups of sugar and been happy with the softer, more caramel-like result; others found it needed extra beating to firm up, or that it set more like caramel than fudge. Sugar is what gives Russian fudge its characteristic grainy-smooth set rather than a glassy caramel one, so halving it will change the texture even if it still tastes good. For the classic “sets every time” result, use the full 4 cups.

This almost always means it came off the heat before reaching true soft-ball stage – the difference between “not set” and “set” is only a couple of degrees in the last few minutes of boiling, so it’s easy to pull it early, especially without a thermometer. You can usually rescue a sticky batch: put it back on low heat with a splash of milk, bring it back to soft-ball stage, then re-beat. Next time, boil until the cold-water test genuinely gives a soft ball rather than stopping at the 20-minute mark – that’s a guide, not the finish line.