There are two types of rasgulla: Bengali rasgulla, also known as white rasgulla, which is simmered paneer (a type of farmers cheese) and Indian and Mauritian rasgulla, or brown rasgulla, which comprises fried milk-and-flour-based dough served in caramelised syrup. You can use any type of milk for both forms except UHT milk.
Heat the milk in a heavy-bottomed pot until it reaches between 195 and 200 degrees Fahrenheit, stirring frequently; if you don't have a thermometer, heat the milk until it foams on top. You need 1/2 gallon, or 1 part, milk to make 6 to 8 rasgulla.
Take the pot of the stove. Stir in 1/2 part lemon juice or white vinegar and a pinch of salt and let the milk coagulate for 10 minutes.
Strain the curds into a sieve lined with a couple layers of cheesecloth set over the sink. If you want to reserve the water -- which is packed with whey protein -- for a beverage, store it in the refrigerator for up to 24 hours.
Bring the cheesecloth together around the paneer and twist it to wring the water from it. Set the paneer aside.
Transfer the paneer to a lightly floured surface and knead it until smooth. Use only 1 teaspoon of flour for dusting the work surface for each batch of rasgulla.
Add a couple pinches, or about 1 teaspoon of flour, for every batch of paneer. Mash the flour into the paneer with the spatula to mix.
Add equal parts sugar and water to a heavy-bottomed pot; you need the sugar water about 2 inches deep. Add whole spices and flavorings -- rosewater and cardamom pods are traditional -- to the water to infuse the rasgulla with aroma while it simmers.
Bring the sugar water to a low simmer. Roll the paneer into 1- to 1/2-inch spheres, or about the size of meatballs. You want a smooth, crack-free surface on the rasgulla.
Lower the rasgulla gently into the simmering water and cover. Simmer the rasgulla for about 10 minutes; turn off the heat and let the rasgulla steam until puffed, about 10 more minutes.
Transfer the rasgulla to a serving dish or storage container and let them reach room temperature. Pour the sugar water over the rasgulla and chill them in the refrigerator for about 1 hour before serving.