This is functionally same as this one: What exactly is this でね construction?
で is usually used to connect to phrases, but when the speaker is too excited about the first part already, s/he wants to affirm it with ね.
- verb's te-form is used here, which is equivalent to noun/na-adj. + で (duh)
- has です in the middle
The seemingly dislocated です is put there to keep politeness (in order to talk to a senpai) which otherwise nowhere to place in this (half-)sentence. Generally, where final particles can be used, it can be buffed with です for politeness even no copula is expected.
This is a colloquial grammar, because use of final particles as such is.