Melt the butter in a large pot set to medium high. Stir in the flour and let toast while stirring continuously.
Add the onions and fry for another 3 minutes until softened.
Slowly pour in the water while continuously whisking. Season with about 1 teaspoon of salt.
Add the potatoes, cover with a lid and reduce to medium. Cook for 5 minutes.
Stir in the carrots and cook for another 5 minutes
Stir in the cauliflower, the milk, and cook for another 5 minutes.
Adjust the consistency by adding a bit more milk or corn starch slurry (see Notre).
Finish with finally chopped dill, chives, and white pepper. Taste and season with more salt.
