Preheat the oven to 200°C (fan 180°C).
Heat olive oil in a pan, sauté garlic, then add spinach until wilted. Season with salt and pepper. Let it cool.
Unroll the puff pastry and spread the spinach mixture evenly on top.
Crumble the feta over the spinach.
Roll the dough up tightly and slice into 1.5 cm thick pieces.
Place rolls on a baking tray lined with parchment. Brush with the beaten egg.
Bake for about 15–18 minutes or until golden brown. Let them cool a bit before serving (if you can wait).