Preheat the oven to 180C/350F/Gas 4.
Place the cheese on the toasted muffin halves and place into the oven for 3-4 minutes, or until the cheese is melted.
Heat the olive oil together with the butter in a pan and add the spinach. Cook for about one minute, or until the spinach is wilted, then season with salt and freshly ground black pepper.
Spoon the spinach onto a serving plate and top with the cheesy muffins.