Prick the potatoes all over with the tip of a sharp knife and rub with olive oil and salt. Put on a baking tray

Cut off the sprouting end of the garlic bulb, revealing the cloves inside. Put the bulb in the middle of the tin foil square, drizzle over a little olive oil, season with a little salt, wrap the bulb in the tin foil, pop the bulb on the same tray. Roast in a hot oven for 45-50 minutes, until the potatoes and garlic are soft on the inside

In a small bowl, beat the Marmite and butter together until combined and fluffy. Lay the butter on a rectangle of parchment paper or cling film, roll the butter into a sausage shape and chill in the fridge or freezer until firm. This quantity will make more than you need for the recipe, but will last in the fridge or freezer for 1 month

Cut the potatoes in half, scoop out the center and squeeze the garlic cloves from the bulb. Use a potato masher to mash the fluffy potato centers with the roasted garlic. Taste and season with salt and pepper if you like

Cut the sprouts in half through the core. Bring a large pot of salted water to the boil. Add the sprouts and blanch for 2 minutes, until slightly softened and vibrant green. Drain the water away and allow to steam dry for a few minutes. Heat a large saucepan over medium heat and add the sprouts. Dry fry them so that char and blacken in a few places. Reduce the heat to low and add a knob of Marmite butter. Baste the sprouts in the butter and set aside

Transfer the mash to a serving plate and smooth over. Top with the Marmite sprouts and a sprinkle of flaky sea salt