Place the puff pastry slices next to each other and let them thaw for about 10 minutes. Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). In the meantime, fry the diced ham in a pan without fat until crispy.
Clean and wash spring onions and cut into fine rings. Coarsely mash blue cheese with a fork, mix with cream cheese. Stir in diced ham and spring onions. Season with salt and pepper.
Whisk eggs and milk in a bowl with a fork. Spread one half of each puff pastry slice with cheese-ham-cream, leaving 1⁄2 cm free from the edge. Brush the edges of the pastry with the egg milk.
Fold the empty puff pastry half over the filling. Press the edges of the dough well together with a fork.
Place the Pop-Tartes on a baking tray lined with baking paper. Brush with the rest of the egg milk and bake in a hot oven for 15-20 minutes. Serve with your favourite ketchup.