Melt half of the butter in a pan over a medium heat, then add the onion and fry until softened, but not coloured. Add the garlic and chicken livers and fry the livers until golden-brown all over and cooked through. Splash in the brandy and mustard powder and season well with salt and freshly ground black pepper. Place the liver mixture and half of the remaining butter into a food processor and blend until smooth. Melt the remaining butter in a clean pan. Skim off the froth and pour the butter over the pâté. Transfer to the fridge to chill then serve the pate` with warm toast and fig jam.