Some milks are better suited to foaming than others. Because the whey proteins are the critical stabilizers, milks that are fortified with added protein—usually reduced-fat and skim milks—are most easily foamed. Full-fat foams, on the other hand, are fuller in texture and flavor. Milk should always be as fresh as possible, since milk that has begun to sour can curdle when heated.
India’s Galaxy of Cooked Milks
For sheer inventiveness with milk itself as the primary ingredient, no country on earth can match India. Its dozens of variations on the theme of cooked-down milk, many of them dating back a thousand years, stem from a simple fact of life in that warm country: the simplest way to keep milk from souring is to boil it repeatedly. Eventually it cooks down to a brown, solid paste with about 10% moisture, 25% lactose, 20% protein and 20% butterfat. Even without added sugar,
khoa is almost a candy, so it makes sense that over time, it and the intermediate concentrations that precede it became the basis for the most widely made Indian milk sweets. Doughnut-like fried gulabjamun and fudge-like burfi are rich in lactose, calcium, and protein: a glass of milk distilled into a morsel.
A second, separate constellation of Indian milk sweets is based on concentrating the milk solids by curdling them with heat and either lime juice or sour whey. The drained curds form a soft, moist mass known as
chhanna, which then becomes the base for a broad range of sweets, notably porous, springy cakes soaked in sweetened milk or syrup ( rasmalai, rasagollah).