Making bao buns

The small boy enjoys cooking and baking and we often cook things together. I've even had one attempt at baking with both small boys together, but I won't be doing that again in a hurry...! Anyway, one of the things we have made recently is Chinese baozi. Bao are steamed buns which my husband and I enjoyed when we travelled in China (before we had the boys) and which the boys both ate happily when we tried to introduce them to dim sum at home. There was quite a lot of nice science discussion involved so I thought I'd write about it as it might give other people ideas for how to bring out the science in everyday baking and cooking.

Weighing ingredients

The first stage in making the bao involved quite a lot of maths, with my son reading the scales as we added ingredients, telling me what numbers he could see and whether we had added enough. We had a bit of an overenthusiastic addition of sugar by the small boy(!) so we ended up doubling the recipe to add more of the other ingredients to get the ratio right! This meant lots more reading our digital scales for the small boy and talking about multiplying things by two (or 'two times' a number).

Reading the scales

The recipe calls for the liquid ingredients to be mixed separately to the dry ingredients, so we played a guessing game about which ones were liquids from the list in the recipe (he correctly guessed water, milk and oil).  We talked about how the liquids take on the shape of the container, which in our case was a plastic jug.

Pouring more carefully than the addition of sugar...

The recipe includes adding yeast (and oddly baking powder too) as a raising agent. We discussed how we use yeast in bread, and it makes carbon dioxide bubbles which form the holes you see in bread when you eat it. We had to leave the dough in a warm place for an hour to make it rise, and it clearly filled more of the bowl.  The small boy was pleased his yeast had worked!

Shaping his bao, complete with holes that went all the way through!

The next stage was filling the bao.  I made some sweet and sour chicken for this, which I don't think is traditional but I thought the boys might eat it.  We also left some unfilled for the little fussy eaters. The small boy wasn't keen on helping as he doesn't like things that feel slimy (like the slime we made...).  However, after he'd watched me make the filled ones, when I said he could make the unfilled ones any shape he wanted he gave them a roll and asked if he could see what happened if he poked holes in them.  I let him merrily poke away with his fingers, and he was pretty pleased with his creations when he put them into the bamboo steamer. 

The small boy's bao creations before steaming

He likes the bamboo steamers I bought as he's quite keen on bamboo since he found out it's what pandas eat. He even convinced me to spend £1.50 on a 'lucky bamboo' (which isn't actually bamboo, but looks like it) last time we were in IKEA as he wanted to feed his cuddly pandas; it's been happily growing on our windowsill ever since. Anyway, I digress, and after we had done some simple multiplication in the form of 'I have two steamer baskets with 3 filled bao, how many do I have in total', and he'd asked me some more multiplication questions, we put some water on to boil.

The small boy is familiar with the idea that water freezes at zero degrees Celcius, but is less familiar with its boiling point. It's not something that lends itself to the same hands-on experimentation by little hands, but he could see bubbles of gas (water vapour) forming in the pan and we talked about how this happens at 100 degrees Celcius. He could also see the bubbles bursting at the surface and the steam (water vapour which is condensing in the cooler air into little water droplets) rising above the pan. We put the steamer in top of the pan and after a few minutes could see the steam coming through the lid. I explained that the bao were being cooked by the hot water vapour coming off the pan. As they cook, the yeast and baking powder make them expand again. He was pleased with the larger size of his creations when they were cooked and could see that his holes had become little dimples.

His bao once steamed

When they'd cooled a little, he tried one and declared them to be delicious. He also found them easy to cut with his knife and fork, and ended up showing me how to cut them into half and into quarters as he ate his way through all three of the ones he shaped! 

All in all, it was a tasty dinner with some stir fried vegetables, and some nice science and maths thrown in to the cooking and eating processes, some of which I'd intentionally drawn out for him, and some which he decided he wanted to explore himself.

In case you want to give the bao a try, our recipe (modified from one I found, to take account of the ingredients we actually had in the cupboard) was:
- mix 220 ml water, 50 ml milk and 25 ml sunflower oil together
- separately, mix 520 g self raising flour, 40 g caster sugar, 7 g instant dried yeast and 1 g salt
- slowly add the liquid mix to the dry ingredients and then knead to form a dough
- sprinkle flour over the dough, brush with sunflower oil and leave to prove under a damp tea towel in a warm place for an hour
- divide into 12 and shape. If you're filling them, squash into a round then leave a thicker middle and squash the outside of the circle so it's thinner then put the filling in the middle and pull the dough up around it, twisting to hold shut. If not filling, either leave as a ball or squash and poke random holes!
- put on paper liner and steam for 15 mins.