Preheat oven to 200ºC. Heat butter in a large non-stick frying pan over a medium heat. Add leeks & garlic, cook stirring for 3-4 minutes or until light golden. Add the flour & cook stirring for 1-2 minutes. Whisk in the milk & wine gradually, ensuring the mixture has no lumps. Add the bay leaves & mustard, bring to the boil & cook stirring for 3-4 minutes or until thickened.
Peel, devein & chop the prawns. Add prawns, lemon, parsley & parmesan & divide mixture between 4 x 1 ½ cup-capacity ovenproof dishes.
Cut 4 rounds from the pastry using the ramekin as a guide. Place pastry on top of ramekins & press to seal. Brush with egg & bake for 10-15 minutes or until the pastry is flaky & golden.
Place the peas, mint jelly, vinegar & mint leaves into a small bowl & toss to combine. Serve prawn pies with minted peas & extra mint jelly. Serves 4.