Using lentils for bolognaise / shepherds pie type sauce

[FusionChefGeoff]

I'm trying a veg and lentil shepherds pie later - I've got red or puy dried lentils and a tonne of 'casserole' type veg eg celery, onions, carrots, squash.

Which lentils would be best or a mix and how do I know how much stock to use to fully cook the lentils?? Kids moan if they have any bite to them so I'm aiming for mush

I sometimes use green lentils. They keep their shape better than red

I came on here to recommend the Jamie Oliver recipe but I see someone has beaten me to it.
It's very good