Add a large knob of butter to a frying pan (I like a stainless steel frying pan) and heat over a medium heat
Once the pan is hot and butter coated, place the burger patties down, leaving space between them. Don’t press the patties with my spatula since that squeezes out juices.
Cook for a few minutes until browned and then turn and cook for a few more minutes until they are cooked through. During cooking this it what made a big difference between the burgers being dry and being moist. Use a spoon to spoon the butter over the burgers while they were cooking, do this continuously while cooking them.
When flipping, use a thin, flexible spatula to gently lift the burger without breaking it. After cooking remove the frying pan, let the burgers rest a few minutes to keep juices inside, if you've used plenty of butter to cook them you can pat them dry with kitchen roll so they aren't too greasy.
In the same pan if you need to add more butter do so and make sure it's melted.
Add sliced pieces of the banana to the frying pan and cook until slightly browned on either side.
Plate up the burgers with slices of banana on top.