Then red lentils are the go - no pre-soaking and they boil up to nothing, just add thickness. Great in soup or any kind of stew. This is the cottage pie filling I made on the weekend:

• onion & garlic fried in oil
• fry 500g mince (added some cornflour so it thickens but optional)
• added some tomato paste (or tin of toms, or some passata - whatever is cheap and tomatoey)
• added 1/2 cup(ish) red lentils
• added some stock power (or gravox)
• added a cup of water

Boiled it up until thick - if you have frozen veg chuck it in at the end. Omit the cornflour and/or up the tomatoes for more of a bolognaise.

That and some mash taters on top - I got about 4-5 good meals