Line a colander with four layers of cheesecloth. Combine milk, salt, and vinegar in a saucepan over medium-low heat, and stir constantly with a silicone spatula until mixture reaches 165°F. Remove the saucepan from the heat and set aside until solid white curds form on the surface, about 2 minutes.

Using a slotted spoon or fine-mesh skimmer, transfer the curds to the prepared colander. Cover the top with plastic wrap and allow to drain for 5–10 minutes for soft, spreadable ricotta, or up to 15–20 minutes for firmer curds (pictured below).