Adverb
In a penetrating manner.
Source: Webster's dictionaryShe looked at me penetratingly. So I suppose you can figure out what happened next. Iggy Pop
Perhaps no economist will ever again so utterly encompass his age as Adam Smith. Certainly none was ever so serene, so devoid of contumacy, so penetratingly critical without rancor, and so optimistic without being utopian. Adam Smith
the author treats his subject penetratingly Source: Internet