A burger is not a burger without MELTED ONION topping.
This recipe cannot be rushed - it needs stove time and gentle heat to mature properly. If you're working against the clock, start the onion sauce before you start on the burgers - it can melt away on the side while you make the burgers.
Sweet white onions make a deliciously gentle onion melt, while brown or red onions are slightly more robust, and will make a stronger tasting melt.
Allow 1 medium sized onion per person.
Slice the onions finely - tip - cut the onions in half lengthwise before you slice (this will give you half-rings) - easier to eat and serve.
Choose a non-stick pan with a lid and working over a medium heat, add a small splash of peanut oil (or any other neutral vegetable oil) and a generous pat of butter (aim for a 15mm cube per onion) and add the sliced onions. Put the lid on the pan and reduce the temperature to low. Let the onions slowly sweat for 20-30 minutes, stirring once or twice. Gradually increase the heat and - over the next 10 minutes or so - gently caramelise the onions.
Season to taste, serve and ENJOY :-)
PS: See the following blog for the simplest recipe to make the best, best burgers...