Heat the water, sugar and peppercorns at a low temperature until the sugar is dissolved to create a syrup.
Cut the onions into slices and place in a glass bowl.
Add the vinegar and syrup to the bowl of onions and leave in the fridge for 24 hours to infuse.
To make the mini burger with Saint Agur, first split the mince and form 8 small meat patties.
Then, heat some butter in a frying pan and fry the burger patties until cooked (2-3 minutes on each side, or until cooked through).
Cut small burger buns in half and butter them & cut the Saint Agur cheese into 8 small triangles.
Next, place a lettuce leaf, the pickled onions, the cooked beef patty and Saint Agur cheese onto the burger buns. Allow the cheese to melt a little on top of the hot meat.
Finally, place the top halves of the burger buns on the cheese and place a wooden skewer through the burgers to keep them in place.