Line a colander with four layers of cheesecloth or two layers of food safe paper towels and set over a large bowl.
Combine the milk, salt, and vinegar if using in a microwave safe bowl. Microwave on high until lightly bubbling around the edges, 4-6 minutes. The milk should register about 165F on an instant read thermometer.
Remove from the microwave and gently stir for 5 seconds. The milk should separate into solid white curds and t translucent liquid whey. If not, microwave for 30 seconds longer, and stir again. If necessary repeat until fully separated.
Using a slotted spoon or strainer, transfer the curds to the prepared colander. Cover the exposed top with plastic wrap and allow to drain until the desired texture is reached.
What you don't eat can be stored in a covered container in the refrigerator for up to 5 days.