Butter beaten with sweetened condensed milk is a dense, sweet cream used in Kyiv cake, Prague cake and “Milk Girl”. The usual failure is splitting: the cream turns curdled or soupy. Almost always the cause is a temperature gap between the butter and the condensed milk.
Ingredients and what each one does
- Butter (not margarine) is the base and gives the shape. Its fat sets in the cold and holds the layer.
- Sweetened condensed milk brings sugar, water and flavour. It is an emulsion that must blend into the fat without separating.
How to make it
- Butter and condensed milk at the same room temperature. The butter should dent under a finger without being oily. Cold butter gives lumps, warm butter gives a soupy cream.
- Beat the butter on medium speed until pale and fluffy. Sign: the colour lightens and the volume grows.
- Add the condensed milk in a thin stream into the already whipped butter, at an unchanged, moderate speed.
- Stop the mixer as soon as the colour is even. Further beating overloads the cream with air and breaks the emulsion.
- If the cream is too soft, chill the bowl for 10 to 15 minutes, then give it a short whip.
- Flavourings such as rum or vanilla go in in small amounts. Alcohol is mostly water, and it can split the cream.
What can go wrong
- Split into curds and liquid. The temperatures differed. To rescue it, warm it gently until the fat melts, cool it again and whip it once more.
- Too runny. The butter or the milk was warm. Chill, then whip.
- Too hard and crumbly. It set in the fridge. Take it out 30 minutes before use and stir.
- Too sweet and heavy. That is the nature of the ratio. A few drops of lemon juice or a thinner layer helps.
Substitutions
Boiled (dulce de leche style) condensed milk gives a caramel flavour and slightly thicker texture, with less water. Margarine is not suitable: its fat content is too low and the cream will not hold.
Storage
In the fridge for up to 5 days. Let it sit at room temperature and stir before using.
