Heat the milk to 87°F. Add the thermophilic culture and stir well. Add propionibacteria and stir for at least 1 minute. Cover and allow to ferment for 15 minutes.
Check temperature and make sure milk is no warmer than 90°F. Stir to homogenize the milk, and slowly fold in the diluted rennet. Using an up-and-down motion with your spoon will ensure that the rennet works its way through all the milk, so you can get the highest possible yield.
Allow the cheese to set for 30 to 45 minutes at 90°F, or until the whey begins to separate from the curd. You should see a layer of mostly clear whey floating on top of the curd, and the curd should be pulling away from the sides of the pot.
Using a long knife, cut the curds into 1/4-inch cubes.
Stir the curd with a whisk, slicing it into small pieces. The pieces should all be roughly the same size.
Keep the curds at 90°F and stir with the wooden spoon, working out the whey, for 35 minutes.
Over the next 25 minutes, slowly heat the curds to 120°F, stirring frequently with your wooden spoon. As you stir, the curds will shrink. Keep the curds at 120°F for 30 minutes. The curds should be small, and if you bite one it should squeak in your teeth. A handful of curds, squeezed into a ball, should fall apart in your hands.
Pour the curds into a press lined with cheesecloth. Work quickly; you do not want your curds to cool. Press at 10 pounds of pressure for 15 minutes.
Using a fresh piece of cheesecloth, flip the cheese and press, again, at 15 pounds of pressure for 30 minutes.
Repeat this process again, at 15 pounds of pressure for 2 hours, rinsing the cheesecloth in clean, cool water each time and hanging to dry.
Finally, press at 20 pounds of pressure for 12 hours, or overnight.
Mix 2 pounds of sea salt with 1 gallon of cold water to make a brine. Place the cheese in the brine and let it soak for 24 hours.
Take the cheese out of the brine and age at 55° to 60°F for one week. Flip and wipe daily with a damp cheesecloth dipped in salt water.
Age the cheese in the kitchen (or another warm room) for 2 to 3 weeks. Flip and wipe daily with a damp cheesecloth dipped in salt water. The cheese should swell and will have a characteristic Swiss cheese smell.
Place the cheese in your aging refrigerator or cheese cave for 12 weeks or more. (Click here for practical methods for aging cheese.) Flip once or twice a week and remove mold with a cheesecloth dipped in salt water.