Line a sieve with a piece of muslin cloth and set this over a large and deep bowl.
In a heavy base pot pour the milk, cream and salt and bring it to the boil while stirring constantly. As it just starts to come to the boil, add the lemon juice and reduce the heat and allow it to simmer for about 2 minutes.
Remove the pot from the heat and let it stand at room temperature for 15 minutes.
Strain it in the sieve and let it stand for 1 hour.
Scrape the ricotta out of the cloth and place in an airtight container in the fridge for not longer than 3 days.