口いっぱいにほおばっておしゃべりしていけません。

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to stuff one's cheeks; to fill one's mouth (with food)

chattering; talk; idle talk; chat; chitchat; gossip; chatty; talkative; chatterbox; blabbermouth