Cut the stalks out of the mushrooms using a small, sharp knife. Chop the stalks into small pieces.
Melt the butter over a medium heat in a medium frying pan (skillet). Add the chopped mushroom stalks, garlic and spring onions and cook, stirring often for 3-4 minutes until the mushroom stalks are tender.
Add the spinach, cream, salt, pepper and cheddar cheese to the pan. Continue to heat, stirring occasionally until the spinach has wilted and cheese has melted (about 3-4 minutes).
Stir in the lemon juice.
Place the mushrooms on a baking tray and spoon in the spinach mixture.
Place the panko breadcrumbs, vegetable oil, parmesan, paprika and chilli flakes in a small bowl and stir until the panko breadcrumbs are coated in the oil.
Spoon the panko mixture on top of the mushrooms.
Place in the oven and cook for 15-20 minutes until the breadcrumbs are golden brown.