Preheat the oven to 200°C
Add the sprouts and some water to a saucepan and bring to the boil. Then lower the heat and let the sprouts simmer for 5 minutes.
Drain the sprouts and put them into an ovenproof dish or baking tray.
Add the Marmite and stock cube to 50ml of boiling water, and stir until dissolved.
Pour the Marmite mixture over the sprouts and toss until they are coated. Spray the sprouts with low-calorie cooking spray.
Place the sprouts in the oven for 10 minutes. Give them a shake and a few extra sprays of spray, then cook for a further 10 minutes — until golden brown around the edges.
Remove from the oven and serve!