Pre-heat your oven to 180C Fan/200C/400F/Gas Mark 6. Take the pastry out of the fridge, un-package it but don't unroll it yet as it will need to come to room temperature before being rolled out otherwise it can crack
Mix the ricotta, egg, parmesan, thyme and lemon together until they form a smooth paste
Roll the pastry out onto a baking tray, if it doesn't come with baking paper make sure the tray is lined with it
Spread the ricotta mixture over the puff pastry sheet, leaving a 1 cm border around the edge
Arrange the asparagus neatly on top, trimming the ends if needed, and sprinkle over some frozen peas. Drizzle a little olive oil over the asparagus
Use a pastry brush dipped in milk to glaze the 1cm border
Bake the tart for around 20-25 minutes, until the pastry is golden and risen
Chop up the mint leaves and sprinkle them over the tart
Serve hot, or allow to cool to room temperature, then refrigerate for up to 2 days. You can re-heat the tart or serve it cold