Plugrà - Cauliflower Gratin

Ingredients

• 2½ pounds cauliflower florets (from 1½ heads of cauliflower)
• 6 tbsp Plugrà salted butter
• 3 tbsp all-purpose flower
• 2 cups milk
• 1 tsp Dijon mustard
• 1¼ tsp Kosher salt
• ⅛ tsp cayenne
• ½ tsp garlic powder
• ½ cup (4 ounces) cream cheese, cut into pieces
• 1 cup (4 ounces) grated sharp white cheddar
• ¼ cup pearled couscous (or Israeli couscous)
• 5 tbsp Plugrà salted butter