Step by step
Peel the onions of their outer sections and roots, then cut out the central core leaving a hole
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.