Pour the milk into a heavy-bottomed pot and bring to 80-90 degrees Fahrenheit. Use a digital thermometer to accurately check the temperature. If using warm, fresh milk, you can bypass heating.

Once the milk has come to temperature, add your mesophilic starter culture by sprinkling it on top of the milk. Wait 5 minutes, then gently stir the culture into the milk. If you have leftover whey from a previous batch, you can use that instead of the starter culture. When using pasteurized milk, after stirring in the culture, take ¼ cup of cold, non-chlorinated water and add the calcium chloride to it. Mix together and then pour into the milk. Gently stir to incorporate. Non-chlorinated water is used to prevent the chlorine from killing the cultures.

Next, get ¼ cup cold water. Add your rennet to the water and stir. Pour the rennet mixture into the milk mixture. Gently stir, for approximately 15-30 seconds. Put the lid on the pot or jar.

Leave the milk on the counter or within the oven for 12-24 hours, or until the milk has set and the curds have separated from the whey. If the house is cold or drafty, I will turn the oven light on and put the pot of milk in the oven overnight.

After the milk has pulled away from the side of the pan, and a clear, yellowish whey has formed, the quark is ready to be strained. To do this, I pour off the whey (save whey for cooking, caramel, and smoothies!) then cut the quark curds into 1” cubes. After that, I transfer the quark to my wet tea towel or muslin piece and tie the diagonal corners. I hang this from the cupboard knobs for around 3-4 hours, ensuring the bag is suspended over a bowl or sink to catch any remaining whey.

After the quark has strained, move the quark to an airtight storage container. Add 1 teaspoon of salt for every gallon of milk and stir well. Then store in the fridge for up to 2 weeks. Glass or plastic containers are both suitable.