应该是 Given are two pie charts. 

属提前 given 后的倒装用法，此处用 are，因为真正的主语是 two pie charts。

类似例句：

Heaped up in one corner was a pile of junk. 堆在一角的是一堆废物。

Buried in the sands was an ancient village. 一个古老的村庄被埋在这沙土之中。

Gone are the days when they could do what they liked. 他们为所欲为的日子一去不复返了。