Set a large sieve over a bowl. Dampen 2 layers of cheese cloth and line the sieve. Pour milk, cream and salt into a large pot (enamel works best) and bring to a full boil over medium heat, stirring occasionally to avoid burning.
Remove from heat and add the vinegar or lemon juice and stir. Let mixture set a couple of minutes to form curds.
Pour the mixture into sieve and let drain (usually about 1/2 hour) periodically removing the liquid from the bowl. The longer it drains the firmer the cheese.
Heat pasta water and cook, drain and pour into pasta bowl add the bolognese sauce, mix well garnish with a dollop of fresh ricotta cheese or freshly grated grana padano.