Cauliflower, Romanesco & Broccoli Gratin

Bring a large pot of water to a boil. Add florets and cook, stirring frequently, for 1 minute. Drain in a colander and immediately rinse with cold water until cool. Drain well. Spread on a baking sheet or kitchen towel and pat with a clean towel to soak up any excess water.

Preheat oven to 375 degrees F. Coat a 9-by-13-inch (or similar-size shallow ovenproof dish) with cooking spray.

Combine milk, mustard, garlic powder and salt in the large pot; bring to a simmer over medium-high heat. Combine cornstarch and water in a small bowl; whisk into the simmering milk. Bring the mixture to a boil over high heat, whisking. Reduce heat to maintain a simmer and cook, whisking, for 2 minutes. Add Cheddar, Gruyere and chives; whisk until smooth. Remove from heat.

Add the florets to the pot and gently stir to coat with the cheese sauce. Transfer to the prepared baking dish. Combine crackers and oil in a small bowl and sprinkle over the vegetables.

Bake until the cheese sauce is bubbling and the florets are starting to brown on top, 25 to 30 minutes. Serve warm.