I've been asked a few times what causes some people's breads/buns to harden when baked. Here are a few tips that might be of some help inshaAllah.
Hard crusts/bread/buns etc means that you are either baking on too low heat and for too long, OR the dough you started off with was not kneaded well enough. So inshaAllah next time when you knead the dough, follow these tips:
1. Make sure the water/milk you use for kneading the dough is warm. Not HOT, but WARM! Hot water kills the yeast so make sure it is finger-tolerable warm.
2. Knead the dough well, for a good 8-10 minutes and get it to an almost sticky consistency, then dab a bit of oil on your palms and apply all over the ball of dough and cover it, let it rest to rise as per the recipe.
3. Make sure you pre-heat the oven before putting the tray of bread/buns in. Putting a tray of buns in a cold oven then turning on the heat whilst it's in there makes them take longer to get done, thereby hardening them in the process.
4. Add a little bit of milk to your egg yolk before brushing over the bread/before baking. The milk helps keep the buns soft and the yolk gives them a good colour.
5. Standard temperature for breads/buns ranges from 180-200 C. So keep your oven in this temp range unless the recipe states otherwise.
6. If your oven has separate functions for top and bottom heating/grills, don't turn on both at once, first use the bottom grill, then midway turn on the top one to even out the colour.
7. Buns take between 12 mins to 20 mins to get done, depending on the size of individual pieces. So if after this time they are not yet sufficiently coloured, you can crank the heat up slightly to speed things along. But keep a close eye on them.
8. Immediately after baking, whilst still hot, brush a bit of butter on the buns, then cover with a kitchen towel to retain moisture and keep them soft.