Season meat with salt and pepper. With each.
Spread mustard and cranberries, roll up and pin. Clean, wash and halve the mushrooms. Peel and finely chop the onion. Bring a good 2 l salted water to the boil.
Heat clarified butter in a casserole. Brown the rolls in it all around. Take them out. Fry the mushrooms and onion in hot frying fat. Season with salt and pepper. Well 1⁄4 l water on, broth stir in and boil up.
Add the rolls and braise everything covered at medium heat for 6-8 minutes.
In the meantime, heat the spaetzle in boiling salted water for 3-4 minutes (see package instructions).
Season the braising stock with salt and pepper.
Drain the spaetzle. Cut the rolls into slices if necessary. Arrange everything. Lamb's lettuce tastes good with it.