Why the buns take two days

The obvious question is why it takes two days when the supermarket manages it in an afternoon.

The short answer is that a supermarket bun is a different product made a different way. The longer answer is more interesting, and it is mostly about sugar, butter and temperature.

An enriched dough is a hostile place to be a yeast

Bread dough is flour, water, salt and something alive. A bun dough adds butter, sugar, milk and egg, and every one of those additions makes life harder for the organisms doing the leavening.

Sugar is the counter-intuitive one. It looks like food, and in small amounts it is. Past roughly a tenth of the flour weight it starts working the other way: dissolved sugar raises the osmotic pressure of the water in the dough, which pulls water back out of the yeast cells and stresses them. This is a real enough problem in commercial baking that there is a whole product category of osmotolerant yeast sold to deal with it.

Butter does two things. It coats the gluten strands, which is what makes an enriched crumb tender and short rather than chewy. That is the accepted explanation and it is in every textbook, though it is usually asserted rather than demonstrated. At high levels it also physically gets between the yeast and everything it needs.

So a cardamom dough is slower than a bread dough before anything else is decided. Add a starter instead of a packet of yeast and it is slower again.

The night in the fridge

It is mixed on the first day and goes cold overnight, somewhere around three or four degrees, for anything from twelve hours to a couple of days.

Below about twenty degrees the yeast largely stops inflating the dough. Enzymes and bacteria do not stop. They carry on at a reduced rate, breaking starches into sugars and proteins into amino acids, producing acids and aromatic compounds, and none of that is inflating anything.

That gap is the whole trick. Flavour accumulates while the dough stays under control. A bun proved warm in three hours has had three hours of flavour development; the same dough held cold overnight has had twelve or more, and has not turned into an over-proved balloon in the meantime. It also leaves more of the sugars and amino acids that brown in the oven, which is why a retarded dough colours better.

And cold dough behaves

My second reason is physical, and it is the one I would not give up even if the flavour were identical.

A kardemummabulle is a twisted, folded thing. The butter in it is what makes those layers separate rather than merge, and butter only does that inside a fairly narrow window of firmness. Too warm and it smears into the dough and the layers disappear. Too cold and it cracks into fragments and tears the sheet. Roll-in fats are specifically formulated to stay workable across roughly ten to thirty-three degrees for this reason, which is a much narrower range than a kitchen goes through in a day.

Cold dough also holds a shape. Gluten under tension wants to spring back, and time in the cold lets that tension relax, so a knot tied in cold dough is still the shape you tied when it comes out of the oven.

Both of those are why the shaping happens on the second morning, on dough straight out of the fridge, and not on the evening it was mixed.

What two days does not buy

It does not make the buns healthier and I am not going to pretend otherwise. Long fermentation does measurable things to wheat, and I have written about what is supported and what is oversold separately. A bun is butter and sugar in any case.

Two days buys flavour and structure. That is a sufficient reason, and it is the true one.