天上掉馅饼

tiān shàng diào xiàn bǐng

a meat pie falls from the sky (idiom)

to have something fall into your lap

天

tiān

day

上

shàng

(bound form) up; upper; above; previous

掉

diào

to fall

馅

xiàn

filling; stuffing (for dumplings, pies etc)

饼

bǐng

round flat cake