Having come across 
(Also I heard some folks like gifs. Gif warning ahead)
Firstly, I discovered some hidden carbs in baking powder. They need an inert chemical to prevent the baking soda and cream of tartar from interacting in the packet and going awful, so they use either rice flour or corn flour. So we up and decided to use the baking soda and cream of tartar in two separate parts and combine at the last possible instant.
Buckle up. It's an adventure.
We decided to use a three-egg mix, rather than go the whole dozen I initially gassed about (take notes, lovely followers. This is going to be important later). Then we separated the whites and the yolks.
I even managed to separate three perfect yolks! Always remember to celebrate life's little victories:
Now here is where the math went wrong. We needed the total volume of butter for three eggs. Hubby read that we'd need 600 ml of butter for a dozen, but forgot it was for twelve eggs, and thought it was for six. So he assumed 100ml per egg.
I asked him if he was sure about that. Three times. I may have mentioned that an egg is an ounce, but that could be 20/20 hindsight.
Since butter has a gram/ml ratio, we went ahead and melted three hundred grams of butter.
The big one on the left of the picture is what we Australians know as a 'stick' of butter. That's two hundred and fifty grams.[1]
While we were melting that enormous load of animal fats, we added two and a half teaspoons of Cream of Tartar to the egg whites and blended it in. We thought
And whipped them up into stiff peaks.
Next, we added the melted butter to the egg yolks in the food processor.
And blitzed it together.
Then added two teaspoons of bi-carb.
Once that was all mixed up, it was time to add the yolk mix to the white mix. VERY SLOWLY.
And a quick grease of the loaf pan...
Before we poured all that noise into the pan.
And put it into the oven, which we of course had pre-heating during this adventure.
It was when it came out that we realised that we'd made a massive mistake...
And the end result was... not bread.
In texture, it was more like a soggy crumpet than anything else. And as for the taste... When warm, it was like scrambled eggs. When cold, it was like scrambled egg with too much baking soda in it. Yuck.
End verdict: I had to toss it into the rubbish. Complete fail.
Post-mortem calculations told us that we should have had roughly eighty-five grams of butter and not, as Hubby said, three hundred. But out of morbid curiosity... where else did we go wrong?
[1] And now we know why so many Australians have trouble with American recipes, because an American stick of butter is roughly a quarter of that.