4 average-sized carrots
A hardish yellow cheese, like Cheddar or Grimbergen, cut into cubes (optional)
Some more butter for frying + olive oil
Salt & fresh ground black pepper
Cut the potatoes into boiling size, so a little bigger than the circle created by your thumb and forefinger. Slice the leek into rings and then in half. While the potatoes are boiling in salted water, fry the leek gently for ten minutes in some butter and olive oil with the sausages, which will give it some flavour, adding some salt and pepper.
Once the potatoes are nicely boiled, put some butter and milk in it, and mash it up into a consistency.
Then add the leek, mixing well. At this point, you can slip in some small blocks of cheese if you want. Serve with sausages and a nice sauce like mayonnaise, pickle or mustard.