How do you narrate your thinking in an interview without either rambling or going dead silent?

I've got two failure modes. Either I go completely quiet while I think and the interviewer has no idea if I'm stuck or cooking, or I over-explain every micro-thought and run out of time.

I know 'communicate your thought process' is the advice, but nobody says how much. What does the good middle actually sound like? Do you state the plan first and then narrate as you code, or something else?