Add cauliflower pieces to the saucepan and cook for 2 minutes.
Pour in the chicken broth, bring to a boil, then reduce heat and simmer until cauliflower is tender.
Preheat the oven to 375°F (190°C).
Carefully transfer the cauliflower mixture to a blender.
Add butter, Dijon mustard, and grated Parmesan cheese.
Blend until smooth to create the sauce.
In a large bowl, gently mix together the chopped hard-boiled eggs, blanched broccoli, 3/4 of the chopped hazelnuts, and cauliflower sauce.
Pour the mixture into a greased baking dish.
Sprinkle the remaining hazelnuts and chopped prosciutto over the top.
Cover the dish with foil.
Bake in the preheated oven for 20 minutes.
Remove the foil and switch the oven to broil.
Broil for about 2 minutes, or until the prosciutto is crispy.
Serve hot.
Notes / Tips / Wine Advice:
Wine Advice:
Pair this creamy and flavorful cauliflower gratin with a light-bodied white wine such as Sauvignon Blanc or Pinot Grigio. The crisp acidity and fruity notes of the wine will complement the richness of the dish without overpowering its delicate flavors.