Step by step
Put a knob of butter in each onion, then fill with the stuffing mixture and finish off with a walnut kernel on top
Tips
If you want to transform a recipe like this to one perfect for vegans, replace the butter with to olive oil and the cheese with one suitable for vegans.
Trivia
If you want to cut your onions without making yourself cry, try this cunning idea: wet the blade of your knife with some water before starting work.