Put the brew kettle into the crafting grid to convert it into the cheese vat.
The cheese vat cooks milk to eventually produce the desired cheese curds.
Place the cheese vat above a heat source, such as fire. Fill the cheese vat with five buckets of milk, one bottle of rennet, and one starter culture. Right click with a sword to 'stir' the contents. It will then begin cooking. Once it has finished there will be plain curds and whey. Take the whey out with a bucket. Add the ingredients that correspond with the desired cheese (See the cheese page for the list of cheeses). Once all the ingredients are added to the vat of curds it will automatically begin cooking again, no sword necessary at this point. Once it has finished cooking, right-click it with a cheese cloth to remove the curds.