Cauliflower Mac 'n' Cheese Casserole

8 cups coarsely chopped cauliflower
2 tsp SIDS SALT & PEPPER, divided
1½ cups whole milk
170 g cream cheese
1½ tsp curry powder
1 tsp SIDS WINE & PEPPER MUSTARD
1¼ cups mozzarella, shredded
1¼ cup sharp cheddar, shredded, plus more for sprinkling
1 tbsp finely chopped chives
Special Equipment 1x 2 litre baking dish

Toss cauliflower and ¼ tsp SIDS SALT & PEPPER in a large microwave-safe bowl. Cover with plastic wrap, pierce plastic with a knife a few times to vent and microwave on HIGH, 10 minutes. Carefully remove plastic and transfer cauliflower to a colander. Cool to room temperature, then transfer to a large bowl.
Meanwhile, cook milk, cream cheese, curry powder, SIDS WINE & PEPPER MUSTARD and remaining SIDS SALT & PEPPER, stirring constantly, until smooth, about 4 minutes. Let cool to room temperature, about 30 minutes. Add cauliflower and toss to combine. Add mozzarella and cheddar and toss to combine—mixture should be cool enough so cheese doesn't melt. Transfer cauliflower mixture to baking dish.
If Baking Immediately:-- preheat oven to 175°C. Cover dish with foil and bake casserole until heated through and just beginning to bubble, about 45 minutes. Remove foil and sprinkle cheddar over. Heat griller and grill until top is browned and bubbling, 2–5 minutes.
If Freezing to Bake Later:-- cover dish with an airtight lid or double layer of plastic wrap and freeze up to 3 months. To cook, preheat oven to 175°C. Cover dish with foil and bake casserole 45 minutes. Remove foil and stir well with a rubber spatula. Continue to bake, uncovered, until just bubbling and heated through, 10–15 minutes more. Sprinkle cheddar over. Heat griller and grill until top is browned and bubbling, 2–5 minutes.
To cook individually portioned frozen casseroles in the microwave, partially cover and microwave on HIGH, 4 minutes. Uncover, stir, and microwave at 1-minute intervals until heated through, 4–5 minutes more.
Top with chives before serving.
Do Ahead: Casserole can be assembled 1 day ahead- cover and chill, or freeze up to 3 months.