Have never tried this with lambs liver, but it works superbly with calves liver and kidneys:

Make very thin crepes, keep warm
Chop onion, fry in butter with some bacon "bits", remove from pan
Slice liver into thin strips ("geschnätzelt") and fry in small batches in butter
Add seasoning to taste (herbs, garlic, pepper whatever)
Make a cream sauce with what's left in the frying pan, add a good dash of cognac or calvados
Fold the liver with generous amounts of the sauce into crepe parcels
Serve with salad