Dulce de Leche

Ingredients

• 1 litre milk
• 350 g sugar
• 0.5 tsp baking soda
• vanilla bean or essence
• 2 glass marbles

Method

Dulce de leche is a slow-cooking exercise in patience and attention. The transformation from thin milk and sugar to dense, caramel-brown spread depends entirely on low, even heat and constant motion — skip either and you'll have a grainy, burnt mess. Combine the milk, sugar, baking soda, and vanilla in a heavy-bottomed pan. The baking soda neutralises the milk's acidity, which prevents curdling at the temperatures you'll reach; it also accelerates browning by raising the pH. Stir until the sugar dissolves completely, roughly 5 minutes at medium heat.

Once dissolved, drop the heat to low — aim for a bare simmer, barely moving on the surface. This is where the glass marbles earn their place: they absorb and distribute heat more evenly than the pan alone, preventing hot spots that scorch the bottom. Stir every 3–4 minutes in the first hour, then every 1–2 minutes as the mixture thickens. You're looking for caramelisation of the milk solids — the colour should deepen from pale cream to tan to deep amber over roughly 90 minutes to 2.5 hours depending on your stove's true output. The mixture will thicken visibly and the surface will develop a slight skin that breaks when you drag a spoon through it. If it boils aggressively, you've overshot the temperature; remove it from heat for a minute and resume at an even lower setting.

In the final 20 minutes, stir almost constantly. The dulce de leche is ready when a spoon dragged across the pan leaves a clean trail that holds for a second before the mixture flows back in. At this point it should resemble condensed milk or thick custard — nothing more. Tip it onto a cold plate and let it cool for 10 minutes; it will thicken further as it cools and the emulsion stabilises. The finished dulce de leche keeps in a sterilised glass jar in the refrigerator for up to three months, though it rarely lasts that long.