01 -
Slice the leeks in half lengthwise, chop into circles, and wash them well.
02 -
Melt the butter, toss in the leeks, and cook gently on low heat for 25 minutes while stirring occasionally.
03 -
Mix in the lemon juice, mustard, and cream. Sprinkle with salt and pepper, then stir it all together.
04 -
Let everything simmer for an extra 10 minutes over low heat.