Preheat the oven to 200ÂșC. Spray 2 x 12-hole mini muffin pans with oil.
Use a 5cm cutter to cut 24 rounds from the pastry. Press the pastry rounds into the prepared pans.
Place a small spoonful of the caramelised onion chutney in the bottom of each pastry case. Top with a little of the feta.
Whisk the eggs, cream and black pepper together in a bowl until well combined. Transfer the mixture to a jug. Pour the egg mixture evenly into the tarts, filling each to just below the top of the pastry.
Top each tart with a little chopped spring onion. Bake for 15-20 minutes in the preheated oven, or until the pastry is golden. Leave the tarts to cool for a few minutes before transferring them to cooling racks.
Tip: You can use your favourite onion marmalade or fruit chutney in place of caramelised onion chutney.