Remove the stems from the mushrooms

Finely chop the stems and the spring onions but keep them separate

In a pan add butter and oil and let it melt until golden. Add the onions and cook for a couple of minutes on their own on medium heat

Add the mushrooms stems and cook for another couple of minutes. Bear in mind that they need to go in the oven so it doesn’t need to be thoroughly cooked

Spoon the onions and stem in each portobello mushrooms and lay thin slices of cheddar on top. Cook for 20 min at 200 degrees