Make the Lazy Sourdough recipe as instructed and allow it to reach a normal good rise on the bench. This will be determined by your kitchen temperature and the weather. When you feel it is looking pretty good, place into the fridge overnight. I made my dough in the morning, left it out for about 4 hours then did a stretch and fold and then put it in the fridge until the next morning.
When you feel the dough is ready to form into a loaf, bring it out from the fridge and prepare a work space with plenty of flour.
Place the cubed butter into the Thermomix bowl (still frozen) and chop 8 sec/speed 10.
Roll or stretch the dough into a rough rectangular shape and flatten slightly.
Spread with about 1/3-1/2 of the chopped butter. Fold each side into the middle of the dough to cover the butter and push down. Turn so that the open edges of the dough are on your left and right sides. Repeat with the butter until you have finished it all and folded it into the dough as much as possible.
Create the round loaf as you normally would and place into the banneton, cover and rise in the fridge for at least another 24H or until you see it is ready to bake.
I didn't preheat the Dutch oven for this recipe as I wanted the butter to stay cold as long as possible. Also no need to preheat the oven.
Place the loaf into a Dutch oven, slash the top, and cover. Place into a cold oven set to 250°C fan forced for 30 minutes.
Remove the lid and reduce the oven temperature to 220°C for a further 35 minutes. The top will be golden and flaky, with lots of surface bubbles. It should still sound hollow when you tap on it. There will be excess butter sizzling around the edges. Allow the loaf to cool in the pan as it will soak up a lot of the butter that has cooked out.
Enjoy, with jams, on its own, but with lots of friends or you will eat it all yourself. It is so good.