• Preheat oven to 425 degrees. Spray a large baking sheet with nonstick cooking spray.

Prepare cauliflower:

• Cut cauliflower into large florets and place on baking sheet.
• Drizzle cauliflower with 1 ½ tbsp. olive oil, then sprinkle with ½ tsp. salt and ¼ tsp. pepper. Mix well.
• Place baking sheet in oven and roast cauliflower until tender, about 15 minutes.

Prepare cheese sauce:

• While cauliflower is roasting, melt butter in a medium skillet over medium high heat.
• Add garlic to butter and saute until fragrant, about 30 seconds.
• Stir flour into butter with a whisk.
• Continue cooking, stirring constantly, until flour mixture is golden, about 2-3 minutes.
• Slowly whisk in 2 cups milk.
• Cook, stirring frequently, until sauce is thickened, about 2-3 minutes.
• Stir 1 ½ cups cheddar cheese into sauce until smooth. (Reserve remaining cheese for assembling gratin.)
• Remove cheese sauce from heat, then season generously to taste with salt and pepper.

Prepare topping:

• Place panko in a small bowl.
• Drizzle with olive oil, then add salt and pepper.
• Stir together well.

Assemble gratin:

• Spray a shallow casserole dish with nonstick cooking spray.
• Add roasted cauliflower to casserole and top with cheese sauce.
  
• Sprinkle remaining ½ cup cheese over sauce, then top with panko.
  
• Place gratin in oven and bake for until browned and bubbly, about 25 minutes.
• Let gratin cool for a few minutes, then sprinkle with parsley and serve. Enjoy!