Slice the onions into 1 cm thick rings.
Cut out the inside to make ring shapes.
Finely chop the onion pieces you cut out.
Dust the onion rings with flour.
Season the pork with salt and pepper, then dust with flour.
Wrap the pork around the onion rings.
Heat the oil in a pan and sear both sides until browned.
Add the chopped onion and the sauce ingredients.
Cover and steam-fry over medium-low heat for 6 minutes.
Add the butter and simmer the sauce down lightly.
