Bring a small pan of water to a simmer and add the vinegar.
Meanwhile, heat a frying pan over a high heat, add the olive oil and fry the black pudding for 5 minutes, turning half way through cooking. When the black pudding is cooked, remove it from the pan and set aside in a warm oven.
Melt the butter in the same pan and fry the mushrooms with a dash of truffle oil.
Meanwhile, crack the eggs into two small bowls. Swirl the simmering water round the pan, reduce to a low heat and carefully place an egg in the centre, allowing the first to set slightly before you add the second. Leave until the whites are set.
Toast the bread and add chopped chives to the fried mushrooms.
Once the eggs are ready, layer bread, mushrooms, black pudding and your poached egg. Enjoy!