Ricotta has been manufactured in Italy since the Bronze Age. It requires only 3 ingredients: full fat milk, salt to taste and vinegar. Sheep, goat or cow milk will do.
Start by warming the milk at medium heat until it reaches 90 degrees Celsius. Make sure not to boil it. And note that you cannot make ricotta with pasteurized milk.
Stir the milk every couple of minutes while heating to avoid a burned crust at the bottom of your pot or pan. After about 15 min, add the salt to taste. Keep stirring with your wooden or silicone spatula. Then when you see the bubbles at the surface of the milk, turn off the heat and add the vinegar. I used white vinegar to keep the white color of the cheese. You can use any type of vinegar you like or even lemon juice. Just make sure to control the acidity because this is what creates the cheese curds.
For every 1 liter of milk, you can add 3-5 tablespoons of vinegar. Every 1 liter of milk will make about 110 grams of ricotta cheese.