Place the puff pastry slices side by side on a baking tray lined with baking paper and allow to thaw
Peel and thinly slice the onions. Heat butter and oil in a pan and fry onions until translucent. Drain anchovy fillets, cut into small pieces and stir in. Season to taste with salt and pepper. Cut goat cheese into 1 cm thick slices
Spread the onion mixture over the dough squares in such a way that an approx. 1 cm wide edge remains free. Place one slice of goat's cheese in the middle of each and bake in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-20 minutes. Serve hot