Preheat oven to 375° F.

Coat an 81⁄2-inch x 81⁄2-inch casserole dish with cooking spray. Set aside.

Steam or blanch cauliflower for 3 minutes; drain thoroughly. Set aside.

In a medium bowl mix together cheese and cornstarch. Set aside.

Place milk and garlic in a large nonstick skillet and bring to a low simmer over medium heat, about 3 minutes.

Reduce heat to low and whisk in cheese mixture a small handful at a time, stirring constantly, until cheese is completely melted, about 2 minutes.

Add cauliflower, 3⁄4 crumbled bacon, green onions, salt, and pepper, and mix well.

Carefully pour mixture into prepared casserole dish. Top with remaining 1⁄4 crumbled bacon and bake for 30 minutes, or until cauliflower is tender and top of casserole has slightly browned.

Divide evenly among four serving bowls and serve immediately, or store refrigerated in an airtight container for up to 3 days.