What could possibly went wrong and turned macaron-to-macalone? Thinking back they were all silly mistakes that should not be happening...
1) The tray position. For my first successful batch, i placed the baking tray on the level just below the middle of the oven. This failure batch was placed right at the middle because T. set up the position and i didnt check it carefully. (damn). After 5 to 6 mins, some show the signature feet so i was happy. But not long after that, like 2 mins, most of the macaron tops started to crack open so as my heart. Nothing could be done to rescue them. I blame myself that i should do a temperature check before i put the whole tray in. For the second tray, i lowered the position to just below the middle level, a more "happy" tray of macarons were made. I wasnt happy with them still, most of them had uneven top and some of them had "half-feet" only, like half of it had feet and the other half didnt. It seems to suggest that it was something to do with temperature that caused the uneven distribution of heat.
2) Icing sugar - while supermarket is selling loads of xmas cake stuff and they have several icing sugar types on the shell. I was in a hurry and picked the "all-in-one" Royal icing sugar which contained egg white powders; whereas the normal icing sugar doesnt! I thought that "egg white powders" would help to balance the moisture in the batter, maybe it does, but not when it is mixed in with the icing sugar.... i really dont know if the icing sugar contents affect the consistency of my failure batch.
3) Oven temperature was not right. At 155C, it took at least 20 mins to bake a tray of small macarons, it was way too long. Most of the resources that i looked at state that it would take around 15 mins... I really need to run a test on temperature.