Roll out pastry to 2.5 mm thick. Cut a 3 cm wide strip from each side of the pastry sheet. Place the trimmed pastry sheet on a baking tray lined with baking paper, then position the 4 strips on the pastry sheet to create a border.
Blanch garlic cloves in a saucepan of boiling water for 5 minutes. Drain, leave until cool enough to handle, then peel; the skins will easily slip off after cooking.
Place peeled garlic in frying pan that just fits the volume of garlic, drizzle generously with olive oil, cover and simmer over low heat for 10–15 minutes or until golden and cooked through. Leave to cool.
Prick the base of the pastry thoroughly with a fork. Refrigerate for several hours, or if you’re in a hurry, pop in the freezer for 15 minutes.
Brush pastry border with beaten egg.
Bake pastry for 20 minutes, then remove from oven and dot with peeled garlic.
Toss olives with orange zest, oregano, rosemary leaves, if using, and a drizzle of olive oil, then scatter evenly over pastry base. Bake for 10 minutes, then reduce oven temperature to 200°C and bake for another 10 minutes or until pastry is deep golden.
Plate spoonfuls of feta over the filling, add a final drizzle of fresh extra virgin olive oil, then scatter with oregano leaves and serve.