Preheat the oven to 400F/200C and coat a small baking tray with olive oil.

Cook the frozen brussels sprouts in the microwave on full power for 4 minutes.

Turn the brussels sprouts out onto a chopping board and slice each one in half lengthways.

Place the halved sprouts into the greased baking tray and add pour over the salt and olive oil. Shake the tray to ensure everything is well coated then bake in the oven for 15 minutes.

After 15 minutes, remove the spouts from the oven, toss them about a bit and bake for a further 5 minutes.

Melt the butter in a saucepan over a medium heat and add in the chopped onion. Cook for 10 minutes, stirring regularly, until the onion is soft and it starts to turn golden brown.

Add in the flour, milk, thyme, onion powder, garlic powder and half of the cheddar cheese. Stir well to make sure all the ingredients are well combined.

Cook the white sauce on a medium heat for 10 minutes, until thickened, then remove the tray of brussels sprouts from the oven and pour the sauce over them.

Return the brussels sprouts to the oven and bake for a further 15 minutes, until the thick sauce has turned golden brown.

Sprinkle over the rest of the grated cheese, top with an extra four brussels sprouts for decoration if you wish and serve.