我迫不及待地想尝尝妈妈做的生日蛋糕(wait)

I can't wait to taste the birthday cake that my mother cooked.
can't wait to do sth. 迫不及待做某事

i cann't wait to taste the birthday cake baked by my mum.

I can't help waiting for having a taste of the cake which is made by my mother.

I can not help to want to taste the birthday cake made by my mom.