Peel and roughly chop the potatoes and carrots (e.g. quarter), cook in the stock for approx. 25 minutes, drain (collect the stock). Mash with a potato masher and pour in the broth again.
Dice the fat bacon and onions. Leave the bacon in a pan, fry the onions until translucent and sweat the flour. Briefly fry the half leek stick cut into strips. Put everything in the stew and let it warm up again. Season to taste with salt, pepper and mustard.