Sift the flour, baking powder and a pinch of salt into a large bowl. Make a well in the centre and add the eggs and milk. Mix together with a handheld electric whisk for 2-3 minutes until smooth. Melt the butter in a large frying pan. Spoon 3-4 large tbsp of the pancake mix into the pan and cook for 2 minutes on each side or until golden and cooked through. Remove from the pan and repeat with the remaining mixture.
Meanwhile, preheat the oven to 200°C/gas mark 6. Preheat the grill to medium. Grill the bacon for 4-5 minutes until crisp and golden. Drain on kitchen paper and chop into small pieces.
Heat the sunflower oil in a frying pan and fry the onion and garlic for 5-6 minutes until softened. Add the spinach, cover and cook gently for 2-3 minutes until just wilted. Stir in the bacon pieces and season with black pepper.
Divide the spinach mixture between the pancakes, then fold each one into a triangle to enclose the filling. Transfer to a baking tray and top each with 25g grated cheese. Bake in the oven for 8-10 minutes until the cheese has melted.