I've been making it this way for about a year but when I recently visited the Kappacasein Dairy
I tasted Bill Oglethorpe's yoghurt made with the starter he uses to make his Comté like cheese Bermondsey Hard Pressed. Now I've started making yoghurt with a cheese culture, as it makes a very delicate French style set yoghurt.
I got my culture as part of the excellent cheese making kit from London cheesemongers Paxton & Whitfield. This costs £45 but it contains everything (cloths, moulds, rennet, starter culture and thermometers) that you need to make both a simple soft and a hard cheddar like cheese. The soft cheeses I made with this kit were very good. Freezing the initial batch of starter means you’ll have enough for at least twenty attempts at a decent cheese or yoghurt after which you can easily buy more culture.
Plain set yoghurt
Take 1 litre of semi skimmed or whole milk (whole milk makes a creamier yoghurt)
100ml of pre prepared cheese starter
1 Kilner jar or large jam jar
Heat the milk slowly, stirring occasionally until you see bubbles appear on the surface and as the froth rises, take it immediately off the heat. Remove from the heat and pour into a basin, allow the milk to cool (the temperature should not fall below 90F/32C.Get your jam jar ready by filling it with hot water, this way the temperature of the milk will be maintained when you pour in your yoghurt mixture.
Whisk the starter with a tablespoon or two of the warmed milk mixture then pour back into the bowl and whisk again. Pour the yoghurt into the jar, seal and wrap the yoghurt pot up in a towel or blanket and place in a warm spot for 8 –12 hours. Don’t jostle the pot if you do your yoghurt may not set.
I use an insulated cool box as I find this way guarantees success every time. Take a small ice box and heat it by filling it with hot water, pour the water out and put the jam jar wrapped in a tea towel inside the insulated cool box. This will make the yoghurt even snugger and imitates a commercial yoghurt-making machine. Also it’s harder to wobble a jar that’s held tightly inside a box.
After it has set you should refrigerate the yoghurt. It will keep in the fridge for about a week.