Cauliflower gratin

Name: Cauliflower gratin
Prep time: 10 min
Cook time: 1 h
Total time: 1 h 10 min
Cuisine: European, Mediterranean, French
Ingredients: 200 g Gruyère cheese or Swiss cheese, cut into pieces (3 cm); 500 g water; 1 cauliflower (approx. 1000 g), cut into florets; 50 g plain flour; 40 g unsalted butter; 500 g milk; ½ tsp salt, plus extra to taste; 2 pinches ground white pepper, plus extra to taste; 1 - 2 pinches ground nutmeg (optional)