This is quick and easy and so tasty!
One each small cauliflower and brocoli. Cut into florets. Try and keep the florets whole. Cook in boiling salted water for a few minutes until cooked but firm. I usually cook for no more than 3-4 minutes. Drain and set aside.
Melt 100g butter in a pot on medium heat. Add 4 heaped tablespoons of flour and cook for a few minutes stirring constantly. Add one litre of milk and whisk until all the lumps dissolve. Keep whisking until sauce thickens. Add some thyme and pepper. Bring sauce to the boil whisking constantly. When sauce has thickened remove from the heat and add 2 teaspoons of fine salt. Whisk in well. I like to add a pinch of nutmeg too - but you can decide if you like the taste. I find if you are using the sauce in a vegetable dish then the nutmeg works.
Add a little of the sauce to an oven proof dish. Add the cooked cauliflower and brocoli. (try and keep the florets facing up). Pour over the remainder of the sauce. Sprinkle with grated cheese. I used a combination of cheddar and parmesan. Bake at 200deg celcius for about 30 minutes until the cheese turns slightly brown.