Hello Farhana, sorry for the late reply. You can get it at Cold Storage/selected NTUCs. Actually you can substitute the buttemilk with milk and vinegar. For every cup of buttermilk, place 1 tbsp of vinegar (lemon juice works too) in 1 cup and add milk to the brim.
Thanks so much Kak. I’m going to try to do the red velvet cake this weekend. I’ve always find the cake so special but yet to taste it. Oh btw, send my regards to yr mum, Mdm Aishah. Tell her it’s from her student at WRSS :)