Twice-Baked Watercress, Goat's Cheese and Hazelnut Soufflé

Name: Twice-Baked Watercress, Goat's Cheese and Hazelnut Soufflé
Prep time: 25 min
Cook time: 1 h 10 min
Total time: 1 h 10 min
Yield: 8 portions
Ingredients: 175 g hard goat's cheese; 50 g blanched hazelnuts; 25 g unsalted butter; 25 g plain flour; 300 g milk; 2 tsp English mustard; 4 medium eggs; 50 g watercress; ½ tsp fine sea salt; water