Make traditional Ricotta cheese using whey left over from cheese making. While not as sweet or creamy as Ricotta made using whole milk, whey Ricotta is a wonderful way to utilize whey that might normally be discarded.
If using both whey and milk, combine the two. Using milk isn't necessary but does substantially increase yield.
Gently heat the milk to 195°F. Stir constantly and consider using a double boiler to prevent scorching. Watch the temperature carefully. While it isn't necessary to be exact, be careful not to let the whey boil as it boils over easily and is very messy.
Remove the whey from the heat and stir in the vinegar. The whey will begin to curdle and some of the curd will rise to the top.
Place a colander in the sink and place the coffee filter (metal reusable filters are best for this) in the colander. Gently pour or spoon the mixture into the coffee filter and allow the whey to drain away. Be careful as much of the curd will likely settle on the bottom of the pot.
Once the pot is empty, allow the ricotta to continue to drain. 1 hour is generally sufficient for a soft ricotta. 6+ hours may be needed for a firmer ricotta.