Whilst you are par-boiling the potatoes, spread some butter around the inside bottom of a ceramic deep oval dish. Once satisified with the potatoes slice them and begin to layer them into the pot. Between each layer lay some spinach, a few knobs of butter, some herbs, cheese and meat if desired, season thoroughly.
Grate some stale bread and mix with the grated cheese and some herbs and wholegrain mustard if desired. Spread mixture on top of pot. Pour 150ml of cream/milk over the potatoes.
Place in the oven at 200 C / Gas 6. Serve with fish or meat and veg.