If serving the dish with potatoes and eggs, start cooking them now.
Divide the cauliflower into medium-large florets and cut the stalk into cubes. Place in a pot with the vegetable broth, bring to a boil, and cook for about 5 minutes or until on the soft side but not mushy. Drain and reserve the broth.
Melt the butter in a large saucepan. Sprinkle the flour on top and let it get some color for about 2 minutes, it should be pale yellow.
Add the milk gradually while whisking continuously, then slowly add the reserved vegetable broth while whisking all the time. Bring to a boil and simmer on medium-low heat for about 3-4 minutes while stirring very often.
Add Dijon mustard. Start with 1 tablespoon and add more according to your taste. Adjust the taste generously with nutmeg, salt, and pepper.
Add the peas and simmer for about 3 minutes stirring often.
Sprinkle with chopped parsley (or dill). Serve immediately with boiled eggs and boiled potatoes.
The nutrition is calculated without the eggs and the potatoes. By adding one egg and 200 g/ 7 oz potatoes per serving, each complete serving will have about 450 calories.