Green Tea Mousse with Red Bean Cheese Cake

Recipe is from the link below (in Chinese):

http://www.rthk.org.hk/elearning/dessert/cake_rbcheesecake.htm

I made this cake before, decided to make it again and see if it will be better than the first time. Still find the mousse is not firm enough. I used 1/2 teaspoon (2g) gelatine as per the recipe, but should use 3/4 teaspoon instead.