Mayonnaise Chocolate Cake

I have always wanted to try this recipe from BH's blog & today, I finally have d time to do it. I think d cake collapsed during baking cause when I removed d aluminum foil, I saw a big hollow gap. But when I turn it over to remove from pan, it's looks GREAT from opp view.. sigh.. guess I need to try this again..

Ingredients

• 110g mayonnaise
• 125ml buttermilk
• 1 tsp vanilla essence
• 120g all-purpose plain flour
• 20g cocoa powder
• 1-1/2 tsp bicarbonate soda
• 110g brown sugar

Method
1.Line a 7" square baking tin with parchment paper (no need to grease).
2.Sift flour, cocoa & bicarbonate soda together.
3.Put sugar & d sifted flour mixture into a bowl.
4.In a separate bowl, mix d mayo, vanilla essence & buttermilk till smooth.
5.Add mayo mixture to d flour & mix till d batter is smooth.
6.Pour mixture into pan & bake at 160 deg C for 20-25 mins.