I made a large pot of 10 grain cereal, and had a lot left over. I've often wondered if I could make muffins with it. So I tried.
I didn't measure anything, just going by what I remember of making muffins, and gauging the texture and appearance by eye. I will do it again, and get specific measurements next time.
To about four cups of cooked and cooled cereal, I added three beaten eggs, 4 tbsp of melted butter, a handful of dried cranberries, some chopped almonds, around 2 tsps of baking powder, and enough flour to give it the consistency of muffin batter (thick, but still pourable). I'd guess I added two cups. The cereal already had some butter and sugar, and was cooked with dried peaches, which dissolved into the porridge when stirred and gave it a wonderful flavor and sweetness. So I didn't add any more sugar.
I spooned half into a silicone giant muffin pan, and the rest I put into a greased loaf pan. During baking, everything puffed up like a popover, and sank down a bit when cooled, which you can see in the photo. At first, I was disappointed, thinking it was a failure. But I accidentally stumbled on something great.
It separated out into layers. The center layer is still porridge, soft and moist, with exactly the texture of thick hot cereal eaten from a bowl. It did not become bready. The cranberries and almonds are mixed all the way through. The cool thing is the other stuff I added separated out into a delicious crust encapsulating the porridge! So you can hold the muffin or slice in your hands, and it's just like holding a muffin. Bite into it, and you have delicious, soft, unctuous hot cereal in the center. The neat thing about the sunken tops is that it creates a perfect reservoir for a spoonful of jam or crème fraîche.
UPDATE: Woke up with my usual dawn-effect blood sugar of 218 (which used to be 250+ before starting the from-scratch project). Did my meds, had coffee with milk and this very slice of porridge bread at 10:30 am, took a reading before lunch, expecting to see 190-240 like that reading has been for so long, and here I am with a stunningly normal blood sugar level of 80.