Heat the olive oil in a skillet over a medium/high heat. Roughly dice the bacon and add to the pan, cooking through until golden. Remove from the skillet with a slotted spoon and set to one side.
Step 2
Melt the butter in the same skillet over a medium heat. Thinly slice the onion and add to the pan, cooking for a minute until lightly golden, then turn the heat down to low and cook gently for a few minutes until soft.
Step 3
Add the vinegar, syrup, salt and pepper. Stir well to combine and continue cooking for a further 2-3 minutes until very soft and starting to caramelized.