Pour the milk, heavy cream, and salt into a large heavy-bottomed pot. Heat over medium heat, stirring occasionally, until it reaches a gentle boil. Reduce heat to low. Add the vinegar or lemon juice gradually while gently stirring. The curds will begin to separate from the whey. Once the curds have formed and the mixture looks curdled, remove from heat. Line a colander with cheesecloth or a fine clean kitchen towel. Carefully pour the mixture into the colander to strain the curds from the whey. Let it drain for 15-20 minutes until desired consistency is achieved. Gather the edges of the cloth and gently squeeze to remove excess liquid. Transfer the ricotta to a bowl and use immediately or refrigerate in an airtight container.