Dilute the rennet and the calcium chloride in 4 tablespoons of cool water each. Mix well and set aside.
Heat the milk to 30 degrees C in a double boiler. Sprinkle the cheese culture on the surface. Allow to dissolve without stirring for a few minutes, then stir well. Cover and keep at 30 degrees C for 1 hour.
Add the calcium chloride; stir for 1 minute. Add the rennet; stir for 1 to 2 minutes. Cover and let sit for 1 hour off the heat.
Meanwhile, prepare the brine: Combine the sea salt, vinegar, calcium chloride and water. Stir well. Set aside.
After 1 hour, check the curds with a palette knife or the back of a spoon, pressing against the edge of the pan. The curds should be firm. Cut into cubes, about 1 to 2cm in size. Gently stir, then let the curds rest for 5 to 10 minutes.
Using a rubber spatula, gently stir for 20 minutes, holding the mixture at 30 degrees C. The curds will gradually sink to the bottom of the pan.
Using a ladle, drain the whey. Discard whey or reserve for another use.
Prepare two basket-style hoops (moulds) by lining with damp muslin or cheesecloth. Ladle the curds into the moulds and fold muslin over top. Place one on top of the other and press lightly. Let the feta drain for several hours (at least 4). While draining, switch the moulds around a few times, and also flip the cheese over within the moulds.
Once cheese is firm, remove from moulds and place into brine. Allow to soak in brine for 8 hours for every 450g of cheese. The cheese can stay in the brine for up to 3 weeks.
To serve, remove from brine and allow the cheese to air dry before serving.