- Preheat oven to 400 degrees F.
- Bring a large pot of salted water to a boil over medium heat. Add the Brussels sprouts and cook for 5 to 7 minutes, until bright green and beginning to soften. Remove the sprouts with a slotted spoon and drop into a bowl of ice water to stop the cooking process.
- Make the sauce by melting the butter and flour together in a saucepan over medium heat. Cook, stirring, until smooth and bubbling, about 1 minute; slowly whisk in milk and continue to cook, whisking frequently, until thick and creamy, 2 to 3 minutes. Season the sauce well with salt and heavily with pepper.
- Place Brussels sprouts in an even layer in a 2 quart baking dish. Pour the sauce over the sprouts and sprinkle the cheese evenly over the top.
- Bake in the center of the oven for 10 to 15 minutes until the top is golden and bubbling.
Source : allrecipes.com