Triple Cheese Sauce Melt the butter in a saucepan over medium-low heat. Stir in the flour. Whisk in a little of the milk at a time, stirring continuously until you have a smooth, thick sauce. Whisk in the mustard. Over a low heat gently fold the cheese through the sauce until fully melted Remove from the heat; season with salt and pepper. Red Onion Relish Melt the butter in a heavy based saucepan with a splash of water Add the onions & cook over a low heat for 15-20 minutes until soft & translucent adding the garlic once the onions are soft. Add the sugar, thyme & season lightly, then cook out until the sugar turns to syrup Add the molasses & vinegar then cook for a further 10-15 minutes over medium heat until the vinegar reduces & the onions have a jam like texture.