Bring a large pot of water to a boil. Add cauliflower and boil for 5 minutes, allowing the cauliflower to soften. With 1 minute remaining, add the frozen corn. Drain the vegetables and set aside.
In a medium sized saucepan add butter over medium high heat. Add flour, stirring until completely smooth. Add milk and 1/2 cup of cheese and continue stirring until cheese is melted and sauce thickens up.
Add cauliflower and corn to a medium sized casserole dish. Pour cheese sauce over vegetables, mixing so cheese covers everything. Sprinkle salt and pepper on top. Add 1 cup remaining cheddar cheese on top.
Place in oven and bake for 30 minutes. After 30 minutes, turn oven to broil and bake (while watching it) for 2-3 minutes, or until cheese is lightly browned.
Want to make it super keto friendly? Substitute chopped up green beans for the corn, heavy cream for the milk and almond flour for the all purpose flour.